critical appraisal meaning in research

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• v.11(5); 2017 May

Critical Appraisal of Clinical Research

Azzam al-jundi.

1 Professor, Department of Orthodontics, King Saud bin Abdul Aziz University for Health Sciences-College of Dentistry, Riyadh, Kingdom of Saudi Arabia.

Salah Sakka

2 Associate Professor, Department of Oral and Maxillofacial Surgery, Al Farabi Dental College, Riyadh, KSA.

Evidence-based practice is the integration of individual clinical expertise with the best available external clinical evidence from systematic research and patient’s values and expectations into the decision making process for patient care. It is a fundamental skill to be able to identify and appraise the best available evidence in order to integrate it with your own clinical experience and patients values. The aim of this article is to provide a robust and simple process for assessing the credibility of articles and their value to your clinical practice.

Introduction

Decisions related to patient value and care is carefully made following an essential process of integration of the best existing evidence, clinical experience and patient preference. Critical appraisal is the course of action for watchfully and systematically examining research to assess its reliability, value and relevance in order to direct professionals in their vital clinical decision making [ 1 ].

Critical appraisal is essential to:

• Combat information overload;
• Identify papers that are clinically relevant;
• Continuing Professional Development (CPD).

Carrying out Critical Appraisal:

Assessing the research methods used in the study is a prime step in its critical appraisal. This is done using checklists which are specific to the study design.

Standard Common Questions:

• What is the research question?
• What is the study type (design)?
• Selection issues.
• What are the outcome factors and how are they measured?
• What are the study factors and how are they measured?
• What important potential confounders are considered?
• What is the statistical method used in the study?
• Statistical results.
• What conclusions did the authors reach about the research question?
• Are ethical issues considered?

The Critical Appraisal starts by double checking the following main sections:

I. Overview of the paper:

• The publishing journal and the year
• The article title: Does it state key trial objectives?
• The author (s) and their institution (s)

The presence of a peer review process in journal acceptance protocols also adds robustness to the assessment criteria for research papers and hence would indicate a reduced likelihood of publication of poor quality research. Other areas to consider may include authors’ declarations of interest and potential market bias. Attention should be paid to any declared funding or the issue of a research grant, in order to check for a conflict of interest [ 2 ].

II. ABSTRACT: Reading the abstract is a quick way of getting to know the article and its purpose, major procedures and methods, main findings, and conclusions.

• Aim of the study: It should be well and clearly written.
• Materials and Methods: The study design and type of groups, type of randomization process, sample size, gender, age, and procedure rendered to each group and measuring tool(s) should be evidently mentioned.
• Results: The measured variables with their statistical analysis and significance.
• Conclusion: It must clearly answer the question of interest.

III. Introduction/Background section:

An excellent introduction will thoroughly include references to earlier work related to the area under discussion and express the importance and limitations of what is previously acknowledged [ 2 ].

-Why this study is considered necessary? What is the purpose of this study? Was the purpose identified before the study or a chance result revealed as part of ‘data searching?’

-What has been already achieved and how does this study be at variance?

-Does the scientific approach outline the advantages along with possible drawbacks associated with the intervention or observations?

IV. Methods and Materials section : Full details on how the study was actually carried out should be mentioned. Precise information is given on the study design, the population, the sample size and the interventions presented. All measurements approaches should be clearly stated [ 3 ].

V. Results section : This section should clearly reveal what actually occur to the subjects. The results might contain raw data and explain the statistical analysis. These can be shown in related tables, diagrams and graphs.

VI. Discussion section : This section should include an absolute comparison of what is already identified in the topic of interest and the clinical relevance of what has been newly established. A discussion on a possible related limitations and necessitation for further studies should also be indicated.

Does it summarize the main findings of the study and relate them to any deficiencies in the study design or problems in the conduct of the study? (This is called intention to treat analysis).

• Does it address any source of potential bias?
• Are interpretations consistent with the results?
• How are null findings interpreted?
• Does it mention how do the findings of this study relate to previous work in the area?
• Can they be generalized (external validity)?
• Does it mention their clinical implications/applicability?
• What are the results/outcomes/findings applicable to and will they affect a clinical practice?
• Does the conclusion answer the study question?
• -Is the conclusion convincing?
• -Does the paper indicate ethics approval?
• -Can you identify potential ethical issues?
• -Do the results apply to the population in which you are interested?
• -Will you use the results of the study?

Once you have answered the preliminary and key questions and identified the research method used, you can incorporate specific questions related to each method into your appraisal process or checklist.

1-What is the research question?

For a study to gain value, it should address a significant problem within the healthcare and provide new or meaningful results. Useful structure for assessing the problem addressed in the article is the Problem Intervention Comparison Outcome (PICO) method [ 3 ].

P = Patient or problem: Patient/Problem/Population:

It involves identifying if the research has a focused question. What is the chief complaint?

E.g.,: Disease status, previous ailments, current medications etc.,

I = Intervention: Appropriately and clearly stated management strategy e.g.,: new diagnostic test, treatment, adjunctive therapy etc.,

C= Comparison: A suitable control or alternative

E.g.,: specific and limited to one alternative choice.

O= Outcomes: The desired results or patient related consequences have to be identified. e.g.,: eliminating symptoms, improving function, esthetics etc.,

The clinical question determines which study designs are appropriate. There are five broad categories of clinical questions, as shown in [ Table/Fig-1 ].

[Table/Fig-1]:

Categories of clinical questions and the related study designs.

2- What is the study type (design)?

The study design of the research is fundamental to the usefulness of the study.

In a clinical paper the methodology employed to generate the results is fully explained. In general, all questions about the related clinical query, the study design, the subjects and the correlated measures to reduce bias and confounding should be adequately and thoroughly explored and answered.

Participants/Sample Population:

Researchers identify the target population they are interested in. A sample population is therefore taken and results from this sample are then generalized to the target population.

The sample should be representative of the target population from which it came. Knowing the baseline characteristics of the sample population is important because this allows researchers to see how closely the subjects match their own patients [ 4 ].

Sample size calculation (Power calculation): A trial should be large enough to have a high chance of detecting a worthwhile effect if it exists. Statisticians can work out before the trial begins how large the sample size should be in order to have a good chance of detecting a true difference between the intervention and control groups [ 5 ].

• Is the sample defined? Human, Animals (type); what population does it represent?
• Does it mention eligibility criteria with reasons?
• Does it mention where and how the sample were recruited, selected and assessed?
• Does it mention where was the study carried out?
• Is the sample size justified? Rightly calculated? Is it adequate to detect statistical and clinical significant results?
• Does it mention a suitable study design/type?
• Is the study type appropriate to the research question?
• Is the study adequately controlled? Does it mention type of randomization process? Does it mention the presence of control group or explain lack of it?
• Are the samples similar at baseline? Is sample attrition mentioned?
• All studies report the number of participants/specimens at the start of a study, together with details of how many of them completed the study and reasons for incomplete follow up if there is any.
• Does it mention who was blinded? Are the assessors and participants blind to the interventions received?
• Is it mentioned how was the data analysed?
• Are any measurements taken likely to be valid?

Researchers use measuring techniques and instruments that have been shown to be valid and reliable.

Validity refers to the extent to which a test measures what it is supposed to measure.

(the extent to which the value obtained represents the object of interest.)

• -Soundness, effectiveness of the measuring instrument;
• -What does the test measure?
• -Does it measure, what it is supposed to be measured?
• -How well, how accurately does it measure?

Reliability: In research, the term reliability means “repeatability” or “consistency”

Reliability refers to how consistent a test is on repeated measurements. It is important especially if assessments are made on different occasions and or by different examiners. Studies should state the method for assessing the reliability of any measurements taken and what the intra –examiner reliability was [ 6 ].

3-Selection issues:

The following questions should be raised:

• - How were subjects chosen or recruited? If not random, are they representative of the population?
• - Types of Blinding (Masking) Single, Double, Triple?
• - Is there a control group? How was it chosen?
• - How are patients followed up? Who are the dropouts? Why and how many are there?
• - Are the independent (predictor) and dependent (outcome) variables in the study clearly identified, defined, and measured?
• - Is there a statement about sample size issues or statistical power (especially important in negative studies)?
• - If a multicenter study, what quality assurance measures were employed to obtain consistency across sites?
• - Are there selection biases?
• • In a case-control study, if exercise habits to be compared:
• - Are the controls appropriate?
• - Were records of cases and controls reviewed blindly?
• - How were possible selection biases controlled (Prevalence bias, Admission Rate bias, Volunteer bias, Recall bias, Lead Time bias, Detection bias, etc.,)?
• • Cross Sectional Studies:
• - Was the sample selected in an appropriate manner (random, convenience, etc.,)?
• - Were efforts made to ensure a good response rate or to minimize the occurrence of missing data?
• - Were reliability (reproducibility) and validity reported?
• • In an intervention study, how were subjects recruited and assigned to groups?
• • In a cohort study, how many reached final follow-up?
• - Are the subject’s representatives of the population to which the findings are applied?
• - Is there evidence of volunteer bias? Was there adequate follow-up time?
• - What was the drop-out rate?
• - Any shortcoming in the methodology can lead to results that do not reflect the truth. If clinical practice is changed on the basis of these results, patients could be harmed.

Researchers employ a variety of techniques to make the methodology more robust, such as matching, restriction, randomization, and blinding [ 7 ].

Bias is the term used to describe an error at any stage of the study that was not due to chance. Bias leads to results in which there are a systematic deviation from the truth. As bias cannot be measured, researchers need to rely on good research design to minimize bias [ 8 ]. To minimize any bias within a study the sample population should be representative of the population. It is also imperative to consider the sample size in the study and identify if the study is adequately powered to produce statistically significant results, i.e., p-values quoted are <0.05 [ 9 ].

4-What are the outcome factors and how are they measured?

• -Are all relevant outcomes assessed?
• -Is measurement error an important source of bias?

5-What are the study factors and how are they measured?

• -Are all the relevant study factors included in the study?
• -Have the factors been measured using appropriate tools?

Data Analysis and Results:

- Were the tests appropriate for the data?

- Are confidence intervals or p-values given?

• How strong is the association between intervention and outcome?
• How precise is the estimate of the risk?
• Does it clearly mention the main finding(s) and does the data support them?
• Does it mention the clinical significance of the result?
• Is adverse event or lack of it mentioned?
• Are all relevant outcomes assessed?
• Was the sample size adequate to detect a clinically/socially significant result?
• Are the results presented in a way to help in health policy decisions?
• Is there measurement error?
• Is measurement error an important source of bias?

Confounding Factors:

A confounder has a triangular relationship with both the exposure and the outcome. However, it is not on the causal pathway. It makes it appear as if there is a direct relationship between the exposure and the outcome or it might even mask an association that would otherwise have been present [ 9 ].

6- What important potential confounders are considered?

• -Are potential confounders examined and controlled for?
• -Is confounding an important source of bias?

7- What is the statistical method in the study?

• -Are the statistical methods described appropriate to compare participants for primary and secondary outcomes?
• -Are statistical methods specified insufficient detail (If I had access to the raw data, could I reproduce the analysis)?
• -Were the tests appropriate for the data?
• -Are confidence intervals or p-values given?
• -Are results presented as absolute risk reduction as well as relative risk reduction?

Interpretation of p-value:

The p-value refers to the probability that any particular outcome would have arisen by chance. A p-value of less than 1 in 20 (p<0.05) is statistically significant.

• When p-value is less than significance level, which is usually 0.05, we often reject the null hypothesis and the result is considered to be statistically significant. Conversely, when p-value is greater than 0.05, we conclude that the result is not statistically significant and the null hypothesis is accepted.

Confidence interval:

Multiple repetition of the same trial would not yield the exact same results every time. However, on average the results would be within a certain range. A 95% confidence interval means that there is a 95% chance that the true size of effect will lie within this range.

8- Statistical results:

• -Do statistical tests answer the research question?

Are statistical tests performed and comparisons made (data searching)?

Correct statistical analysis of results is crucial to the reliability of the conclusions drawn from the research paper. Depending on the study design and sample selection method employed, observational or inferential statistical analysis may be carried out on the results of the study.

It is important to identify if this is appropriate for the study [ 9 ].

• -Was the sample size adequate to detect a clinically/socially significant result?
• -Are the results presented in a way to help in health policy decisions?

Clinical significance:

Statistical significance as shown by p-value is not the same as clinical significance. Statistical significance judges whether treatment effects are explicable as chance findings, whereas clinical significance assesses whether treatment effects are worthwhile in real life. Small improvements that are statistically significant might not result in any meaningful improvement clinically. The following questions should always be on mind:

• -If the results are statistically significant, do they also have clinical significance?
• -If the results are not statistically significant, was the sample size sufficiently large to detect a meaningful difference or effect?

9- What conclusions did the authors reach about the study question?

Conclusions should ensure that recommendations stated are suitable for the results attained within the capacity of the study. The authors should also concentrate on the limitations in the study and their effects on the outcomes and the proposed suggestions for future studies [ 10 ].

• -Are the questions posed in the study adequately addressed?
• -Are the conclusions justified by the data?
• -Do the authors extrapolate beyond the data?
• -Are shortcomings of the study addressed and constructive suggestions given for future research?
• -Bibliography/References:

Do the citations follow one of the Council of Biological Editors’ (CBE) standard formats?

10- Are ethical issues considered?

If a study involves human subjects, human tissues, or animals, was approval from appropriate institutional or governmental entities obtained? [ 10 , 11 ].

Critical appraisal of RCTs: Factors to look for:

• Allocation (randomization, stratification, confounders).
• Follow up of participants (intention to treat).
• Data collection (bias).
• Sample size (power calculation).
• Presentation of results (clear, precise).
• Applicability to local population.

[ Table/Fig-2 ] summarizes the guidelines for Consolidated Standards of Reporting Trials CONSORT [ 12 ].

[Table/Fig-2]:

Summary of the CONSORT guidelines.

Critical appraisal of systematic reviews: provide an overview of all primary studies on a topic and try to obtain an overall picture of the results.

In a systematic review, all the primary studies identified are critically appraised and only the best ones are selected. A meta-analysis (i.e., a statistical analysis) of the results from selected studies may be included. Factors to look for:

• Literature search (did it include published and unpublished materials as well as non-English language studies? Was personal contact with experts sought?).
• Quality-control of studies included (type of study; scoring system used to rate studies; analysis performed by at least two experts).
• Homogeneity of studies.

[ Table/Fig-3 ] summarizes the guidelines for Preferred Reporting Items for Systematic reviews and Meta-Analyses PRISMA [ 13 ].

[Table/Fig-3]:

Summary of PRISMA guidelines.

Critical appraisal is a fundamental skill in modern practice for assessing the value of clinical researches and providing an indication of their relevance to the profession. It is a skills-set developed throughout a professional career that facilitates this and, through integration with clinical experience and patient preference, permits the practice of evidence based medicine and dentistry. By following a systematic approach, such evidence can be considered and applied to clinical practice.

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What is Critical Appraisal?

Critical Appraisal is the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context. It is an essential skill for evidence-based medicine because it allows people to find and use research evidence reliably and efficiently. All of us would like to enjoy the best possible health we can. To achieve this, we need reliable information about what might harm or help us when we make healthcare decisions.

Why is Critical Appraisal important?

Critical appraisal skills are important as they enable you to assess systematically the trustworthiness, relevance and results of published papers. Where an article is published, or who wrote it should not be an indication of its trustworthiness and relevance.

Randomised Controlled Trials (RCTs): An experiment that randomises participants into two groups: one that receives the treatment and another that serves as the control. RCTs are often used in healthcare to test the efficacy of different treatments.

Learn more about how to critically appraise an RCT.

Systematic Reviews : A thorough and structured analysis of all relevant studies on a particular research question. These are often used in evidence-based practice to evaluate the effects of health and social interventions.

Discover what systematic reviews are, and why they are important .

Cohort Studies : This is an observational study where two or more groups (cohorts) of individuals are followed over time and their outcomes are compared. It's used often in medical research to investigate the potential causes of disease.

Learn more about cohort studies .

Case-Control Studies : This is an observational study where two groups differing in outcome are identified and compared on the basis of some supposed causal attribute. These are often used in epidemiological research.

Check out this article to better understand what a case-control study is in research .

Cross-Sectional Studies : An observational study that examines the relationship between health outcomes and other variables of interest in a defined population at a single point in time. They're useful for determining prevalence and risk factors.

Discover what a cross-sectonal study is and when to use one .

Qualitative Research : An in-depth analysis of a phenomenon based on unstructured data, such as interviews, observations, or written material. It's often used to gain insights into behaviours, value systems, attitudes, motivations, or culture.

This guide will help you increase your knowledge of qualitative research .

Economic Evaluation : A comparison of two or more alternatives in terms of their costs and consequences. Often used in healthcare decision making to maximise efficiency and equity.

Diagnostic Studies : Evaluates the performance of a diagnostic test in predicting the presence or absence of a disease. It is commonly used to validate the accuracy and utility of a new diagnostic procedure.

Case Series : Describes characteristics of a group of patients with a particular disease or who have undergone a specific procedure. Used in clinical medicine to present preliminary observations.

Case Studies : Detailed examination of a single individual or group. Common in psychology and social sciences, this can provide in-depth understanding of complex phenomena in their real-life context.

Aren’t we already doing it?

To some extent, the answer to this question is “yes”. Evidence-based journals can give us reliable, relevant summaries of recent research; guidelines, protocols, and pathways can synthesise the best evidence and present it in the context of a clinical problem. However, we still need to be able to assess research quality to be able to adapt what we read to what we do.

There are still significant gaps in access to evidence.

The main issues we need to address are:

Health and Social Care provision must be based on sound decisions.

In order to make well-informed and sensible choices, we need evidence that is rigorous in methodology and robust in findings.

What types of questions does a critical appraisal encourage you to ask?

• What is the main objective of the research?
• Who conducted the research and are they reputable?
• How was the research funded? Are there any potential conflicts of interest?
• How was the study designed?
• Was the sample size large enough to provide accurate results?
• Were the participants or subjects selected appropriately?
• What data collection methods were used and were they reliable and valid?
• Was the data analysed accurately and rigorously?
• Were the results and conclusions drawn directly from the data or were there assumptions made?
• Can the findings be generalised to the broader population?
• How does this research contribute to existing knowledge in this field?
• Were ethical standards maintained throughout the study?
• Were any potential biases accounted for in the design, data collection or data analysis?
• Have the researchers made suggestions for future research based on their findings?
• Are the findings of the research replicable?
• Are there any implications for policy or practice based on the research findings?
• Were all aspects of the research clearly explained and detailed?

How do you critically appraise a paper?

Critically appraising a paper involves examining the quality, validity, and relevance of a published work to identify its strengths and weaknesses.

This allows the reader to judge its trustworthiness and applicability to their area of work or research. Below are general steps for critically appraising a paper:

Decide how trustworthy a piece of research is (Validity)

• Determine what the research is telling us (Results)
• Weigh up how useful the research will be in your context (Relevance)

You need to understand the research question, do a methodology evaluation, analyse the results, check the conclusion and review the implications and limitations.

That's just a quick summary but we provide a range of in-depth  training courses  and  workshops  to help you improve your knowledge around how to successfully perform critical appraisals so book onto one today or contact us for more information.

Is Critical Appraisal In Research Different To Front-Line Usage In Nursing, Etc?

Critical appraisal in research is different from front-line usage in nursing.

Critical appraisal in research involves a careful analysis of a study's methodology, results, and conclusions to assess the quality and validity of the study. This helps researchers to determine if the study's findings are robust, reliable and applicable in their own research context. It requires a specific set of skills including understanding of research methodology, statistics, and evidence-based practices.

Front-line usage in nursing refers to the direct application of evidence-based practice and research findings in patient care settings. Nurses need to appraise the evidence critically too but their focus is on the direct implications of the research on patient care and health outcomes. The skills required here would be the ability to understand the clinical implications of research findings, communicate these effectively to patients, and incorporate these into their practice.

Both require critical appraisal but the purpose, context, and skills involved are different. Critical appraisal in research is more about evaluating research for validity and reliability whereas front-line usage in nursing is about effectively applying valid and reliable research findings to improve patient care.

How do you know if you're performing critical appraisals correctly?

Thorough Understanding : You've thoroughly read and understood the research, its aims, methodology, and conclusions. You should also be aware of the limitations or potential bias in the research.

Using a Framework or Checklist : Various frameworks exist for critically appraising research (including CASP’s own!). Using these can provide structure and make sure all key points are considered. By keeping a record of your appraisal you will be able to show your reasoning behind whether you’ve implemented a decision based on research.

Identifying Research Methods : Recognising the research design, methods used, sample size, and how data was collected and analysed are crucial in assessing the research's validity and reliability.

Checking Results and Conclusions : Check if the conclusions drawn from the research are justified by the results and data provided, and if any biases could have influenced these conclusions.

Relevance and applicability : Determine if the research's results and conclusions can be applied to other situations, particularly those relevant to your context or question.

Updating Skills : Continually updating your skills in research methods and statistical analysis will improve your confidence and ability in critically appraising research.

Finally, getting feedback from colleagues or mentors on your critical appraisals can also provide a good check on how well you're doing. They can provide an additional perspective and catch anything you might have missed. If possible, we would always recommend doing appraisals in small groups or pairs, working together is always helpful for another perspective, or if you can – join and take part in a journal club.

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Best Practice for Literature Searching

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• What are literature reviews?
• Hierarchies of evidence
• 1. Managing references
• 2. Defining your research question
• 3. Where to search
• 4. Search strategy
• 5. Screening results
• 6. Paper acquisition
• 7. Critical appraisal
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What is critical appraisal?

We critically appraise information constantly, formally or informally, to determine if something is going to be valuable for our purpose and whether we trust the content it provides.

In the context of a literature search, critical appraisal is the process of systematically evaluating and assessing the research you have found in order to determine its quality and validity. It is essential to evidence-based practice.

More formally, critical appraisal is a systematic evaluation of research papers in order to answer the following questions:

• Does this study address a clearly focused question?
• Did the study use valid methods to address this question?
• Are there factors, based on the study type, that might have confounded its results?
• Are the valid results of this study important?
• What are the confines of what can be concluded from the study?
• Are these valid, important, though possibly limited, results applicable to my own research?

What is quality and how do you assess it?

In research we commissioned in 2018, researchers told us that they define ‘high quality evidence’ by factors such as:

• Publication in a journal they consider reputable or with a high Impact Factor.
• The peer review process, coordinated by publishers and carried out by other researchers.
• Research institutions and authors who undertake quality research, and with whom they are familiar.

In other words, researchers use their own experience and expertise to assess quality.

However, students and early career researchers are unlikely to have built up that level of experience, and no matter how experienced a researcher is, there are certain times (for instance, when conducting a systematic review) when they will need to take a very close look at the validity of research articles.

There are checklists available to help with critical appraisal.  The checklists outline the key questions to ask for a specific study design.  Examples can be found in the  Critical Appraisal  section of this guide, and the Further Resources section.  

You may also find it beneficial to discuss issues such as quality and reputation with:

• Your principal investigator (PI)
• Your supervisor or other senior colleagues
• Journal clubs. These are sometimes held by faculty or within organisations to encourage researchers to work together to discover and critically appraise information.
• Topic-specific working groups

The more you practice critical appraisal, the quicker and more confident you will become at it.

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• Published: 20 January 2009

How to critically appraise an article

• Jane M Young 1 &
• Michael J Solomon 2  

Nature Clinical Practice Gastroenterology & Hepatology volume  6 ,  pages 82–91 ( 2009 ) Cite this article

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Critical appraisal is a systematic process used to identify the strengths and weaknesses of a research article in order to assess the usefulness and validity of research findings. The most important components of a critical appraisal are an evaluation of the appropriateness of the study design for the research question and a careful assessment of the key methodological features of this design. Other factors that also should be considered include the suitability of the statistical methods used and their subsequent interpretation, potential conflicts of interest and the relevance of the research to one's own practice. This Review presents a 10-step guide to critical appraisal that aims to assist clinicians to identify the most relevant high-quality studies available to guide their clinical practice.

Critical appraisal is a systematic process used to identify the strengths and weaknesses of a research article

Critical appraisal provides a basis for decisions on whether to use the results of a study in clinical practice

Different study designs are prone to various sources of systematic bias

Design-specific, critical-appraisal checklists are useful tools to help assess study quality

Assessments of other factors, including the importance of the research question, the appropriateness of statistical analysis, the legitimacy of conclusions and potential conflicts of interest are an important part of the critical appraisal process

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Druss BG and Marcus SC (2005) Growth and decentralisation of the medical literature: implications for evidence-based medicine. J Med Libr Assoc 93 : 499–501

PubMed   PubMed Central   Google Scholar  

Glasziou PP (2008) Information overload: what's behind it, what's beyond it? Med J Aust 189 : 84–85

PubMed   Google Scholar  

Last JE (Ed.; 2001) A Dictionary of Epidemiology (4th Edn). New York: Oxford University Press

Google Scholar  

Sackett DL et al . (2000). Evidence-based Medicine. How to Practice and Teach EBM . London: Churchill Livingstone

Guyatt G and Rennie D (Eds; 2002). Users' Guides to the Medical Literature: a Manual for Evidence-based Clinical Practice . Chicago: American Medical Association

Greenhalgh T (2000) How to Read a Paper: the Basics of Evidence-based Medicine . London: Blackwell Medicine Books

MacAuley D (1994) READER: an acronym to aid critical reading by general practitioners. Br J Gen Pract 44 : 83–85

CAS   PubMed   PubMed Central   Google Scholar  

Hill A and Spittlehouse C (2001) What is critical appraisal. Evidence-based Medicine 3 : 1–8 [ http://www.evidence-based-medicine.co.uk ] (accessed 25 November 2008)

Public Health Resource Unit (2008) Critical Appraisal Skills Programme (CASP) . [ http://www.phru.nhs.uk/Pages/PHD/CASP.htm ] (accessed 8 August 2008)

National Health and Medical Research Council (2000) How to Review the Evidence: Systematic Identification and Review of the Scientific Literature . Canberra: NHMRC

Elwood JM (1998) Critical Appraisal of Epidemiological Studies and Clinical Trials (2nd Edn). Oxford: Oxford University Press

Agency for Healthcare Research and Quality (2002) Systems to rate the strength of scientific evidence? Evidence Report/Technology Assessment No 47, Publication No 02-E019 Rockville: Agency for Healthcare Research and Quality

Crombie IK (1996) The Pocket Guide to Critical Appraisal: a Handbook for Health Care Professionals . London: Blackwell Medicine Publishing Group

Heller RF et al . (2008) Critical appraisal for public health: a new checklist. Public Health 122 : 92–98

Article   Google Scholar  

MacAuley D et al . (1998) Randomised controlled trial of the READER method of critical appraisal in general practice. BMJ 316 : 1134–37

Article   CAS   Google Scholar  

Parkes J et al . Teaching critical appraisal skills in health care settings (Review). Cochrane Database of Systematic Reviews 2005, Issue 3. Art. No.: cd001270. 10.1002/14651858.cd001270

Mays N and Pope C (2000) Assessing quality in qualitative research. BMJ 320 : 50–52

Hawking SW (2003) On the Shoulders of Giants: the Great Works of Physics and Astronomy . Philadelphia, PN: Penguin

National Health and Medical Research Council (1999) A Guide to the Development, Implementation and Evaluation of Clinical Practice Guidelines . Canberra: National Health and Medical Research Council

US Preventive Services Taskforce (1996) Guide to clinical preventive services (2nd Edn). Baltimore, MD: Williams & Wilkins

Solomon MJ and McLeod RS (1995) Should we be performing more randomized controlled trials evaluating surgical operations? Surgery 118 : 456–467

Rothman KJ (2002) Epidemiology: an Introduction . Oxford: Oxford University Press

Young JM and Solomon MJ (2003) Improving the evidence-base in surgery: sources of bias in surgical studies. ANZ J Surg 73 : 504–506

Margitic SE et al . (1995) Lessons learned from a prospective meta-analysis. J Am Geriatr Soc 43 : 435–439

Shea B et al . (2001) Assessing the quality of reports of systematic reviews: the QUORUM statement compared to other tools. In Systematic Reviews in Health Care: Meta-analysis in Context 2nd Edition, 122–139 (Eds Egger M. et al .) London: BMJ Books

Chapter   Google Scholar  

Easterbrook PH et al . (1991) Publication bias in clinical research. Lancet 337 : 867–872

Begg CB and Berlin JA (1989) Publication bias and dissemination of clinical research. J Natl Cancer Inst 81 : 107–115

Moher D et al . (2000) Improving the quality of reports of meta-analyses of randomised controlled trials: the QUORUM statement. Br J Surg 87 : 1448–1454

Shea BJ et al . (2007) Development of AMSTAR: a measurement tool to assess the methodological quality of systematic reviews. BMC Medical Research Methodology 7 : 10 [10.1186/1471-2288-7-10]

Stroup DF et al . (2000) Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) group. JAMA 283 : 2008–2012

Young JM and Solomon MJ (2003) Improving the evidence-base in surgery: evaluating surgical effectiveness. ANZ J Surg 73 : 507–510

Schulz KF (1995) Subverting randomization in controlled trials. JAMA 274 : 1456–1458

Schulz KF et al . (1995) Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA 273 : 408–412

Moher D et al . (2001) The CONSORT statement: revised recommendations for improving the quality of reports of parallel group randomized trials. BMC Medical Research Methodology 1 : 2 [ http://www.biomedcentral.com/ 1471-2288/1/2 ] (accessed 25 November 2008)

Rochon PA et al . (2005) Reader's guide to critical appraisal of cohort studies: 1. Role and design. BMJ 330 : 895–897

Mamdani M et al . (2005) Reader's guide to critical appraisal of cohort studies: 2. Assessing potential for confounding. BMJ 330 : 960–962

Normand S et al . (2005) Reader's guide to critical appraisal of cohort studies: 3. Analytical strategies to reduce confounding. BMJ 330 : 1021–1023

von Elm E et al . (2007) Strengthening the reporting of observational studies in epidemiology (STROBE) statement: guidelines for reporting observational studies. BMJ 335 : 806–808

Sutton-Tyrrell K (1991) Assessing bias in case-control studies: proper selection of cases and controls. Stroke 22 : 938–942

Knottnerus J (2003) Assessment of the accuracy of diagnostic tests: the cross-sectional study. J Clin Epidemiol 56 : 1118–1128

Furukawa TA and Guyatt GH (2006) Sources of bias in diagnostic accuracy studies and the diagnostic process. CMAJ 174 : 481–482

Bossyut PM et al . (2003)The STARD statement for reporting studies of diagnostic accuracy: explanation and elaboration. Ann Intern Med 138 : W1–W12

STARD statement (Standards for the Reporting of Diagnostic Accuracy Studies). [ http://www.stard-statement.org/ ] (accessed 10 September 2008)

Raftery J (1998) Economic evaluation: an introduction. BMJ 316 : 1013–1014

Palmer S et al . (1999) Economics notes: types of economic evaluation. BMJ 318 : 1349

Russ S et al . (1999) Barriers to participation in randomized controlled trials: a systematic review. J Clin Epidemiol 52 : 1143–1156

Tinmouth JM et al . (2004) Are claims of equivalency in digestive diseases trials supported by the evidence? Gastroentrology 126 : 1700–1710

Kaul S and Diamond GA (2006) Good enough: a primer on the analysis and interpretation of noninferiority trials. Ann Intern Med 145 : 62–69

Piaggio G et al . (2006) Reporting of noninferiority and equivalence randomized trials: an extension of the CONSORT statement. JAMA 295 : 1152–1160

Heritier SR et al . (2007) Inclusion of patients in clinical trial analysis: the intention to treat principle. In Interpreting and Reporting Clinical Trials: a Guide to the CONSORT Statement and the Principles of Randomized Controlled Trials , 92–98 (Eds Keech A. et al .) Strawberry Hills, NSW: Australian Medical Publishing Company

National Health and Medical Research Council (2007) National Statement on Ethical Conduct in Human Research 89–90 Canberra: NHMRC

Lo B et al . (2000) Conflict-of-interest policies for investigators in clinical trials. N Engl J Med 343 : 1616–1620

Kim SYH et al . (2004) Potential research participants' views regarding researcher and institutional financial conflicts of interests. J Med Ethics 30 : 73–79

Komesaroff PA and Kerridge IH (2002) Ethical issues concerning the relationships between medical practitioners and the pharmaceutical industry. Med J Aust 176 : 118–121

Little M (1999) Research, ethics and conflicts of interest. J Med Ethics 25 : 259–262

Lemmens T and Singer PA (1998) Bioethics for clinicians: 17. Conflict of interest in research, education and patient care. CMAJ 159 : 960–965

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Young, J., Solomon, M. How to critically appraise an article. Nat Rev Gastroenterol Hepatol 6 , 82–91 (2009). https://doi.org/10.1038/ncpgasthep1331

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Critical Appraisal : What is critical appraisal?

• What is critical appraisal?
• Where to start
• Education and childhood studies
• Occupational Therapy
• Physiotherapy
• Interpreting statistics
• Further reading and resources

Introduction

Critical appraisal is an essential step in any evidence based process and it is defined by CASP as "t he process of assessing and interpreting evidence by systematically considering its validity , results and relevance ".

The hierarchy of evidence pyramid below provides a means to visualise the levels of evidence as well as the amount of evidence available. Systematic reviews and meta-analyses are the highest level of evidence therefore they are at the top of the pyramid but they are also the least common because they are based on the studies below them.  Moving down the pyramid, the amount of studies increases but the level of evidence decreases. The use of the hierarchy of evidence pyramid is not enough to determine the quality of research because study types can vary in quality whether it is a systematic review or a case study therefore critical appraisal skills are required to evaluate all types of evidence regardless of their level. It is important to apply your own critical appraisal skills when you evaluate research studies to decide if they merit being considered or used as reliable sources of information. Some studies have found that many research findings in published articles may in fact be false  ( Ioannidis, 2005 ).  In the worst cases, some researchers may commit research fraud to acquire research grants  ( Harvey, 2020 ).

Image from https://www.pinterest.co.uk/pin/246361042093714264/

Critical appraisal involves using a set of systematic techniques that enable you to evaluate the quality of published research including the research methodology, potential bias, strengths and weaknesses and, ultimately, its trustworthiness. It is often the case that even peer-reviewed research can have methodological flaws, incorrectly interpret data, draw incorrect conclusions or exaggerate findings. A uthors' affiliations, funding sources, study design flaws, sample size and potential bias are only some of the factors that can lead you to include poor quality research in your own work if not addressed through critical appraisal.

Critical appraisal often involves the  use of checklists to guide you to look out for specific areas in the appraisal process. Checklists vary according to types of research or study designs you are evaluating.

It is important therefore that you possess a good knowledge of research methods in your field of study and a good basic understanding of statistics where statistical analysis is involved.

Please see read  What is critical appraisal?   and see the resources on this page for further information on critical appraisal.

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Tools for Critical Appraisal of Studies

“The purpose of critical appraisal is to determine the scientific merit of a research report and its applicability to clinical decision making.” 1 Conducting a critical appraisal of a study is imperative to any well executed evidence review, but the process can be time consuming and difficult. 2 The critical appraisal process requires “a methodological approach coupled with the right tools and skills to match these methods is essential for finding meaningful results.” 3 In short, it is a method of differentiating good research from bad research.

Critical Appraisal by Study Design (featured tools)

• Non-RCTs or Observational Studies
• Diagnostic Accuracy
• Animal Studies
• Qualitative Research
• Tool Repository
• AMSTAR 2 The original AMSTAR was developed to assess the risk of bias in systematic reviews that included only randomized controlled trials. AMSTAR 2 was published in 2017 and allows researchers to “identify high quality systematic reviews, including those based on non-randomised studies of healthcare interventions.” 4 more... less... AMSTAR 2 (A MeaSurement Tool to Assess systematic Reviews)
• ROBIS ROBIS is a tool designed specifically to assess the risk of bias in systematic reviews. “The tool is completed in three phases: (1) assess relevance(optional), (2) identify concerns with the review process, and (3) judge risk of bias in the review. Signaling questions are included to help assess specific concerns about potential biases with the review.” 5 more... less... ROBIS (Risk of Bias in Systematic Reviews)
• BMJ Framework for Assessing Systematic Reviews This framework provides a checklist that is used to evaluate the quality of a systematic review.
• CASP Checklist for Systematic Reviews This CASP checklist is not a scoring system, but rather a method of appraising systematic reviews by considering: 1. Are the results of the study valid? 2. What are the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CEBM Systematic Reviews Critical Appraisal Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance, and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• JBI Critical Appraisal Tools, Checklist for Systematic Reviews JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• NHLBI Study Quality Assessment of Systematic Reviews and Meta-Analyses The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. more... less... NHLBI (National Heart, Lung, and Blood Institute)
• RoB 2 RoB 2 “provides a framework for assessing the risk of bias in a single estimate of an intervention effect reported from a randomized trial,” rather than the entire trial. 6 more... less... RoB 2 (revised tool to assess Risk of Bias in randomized trials)
• CASP Randomised Controlled Trials Checklist This CASP checklist considers various aspects of an RCT that require critical appraisal: 1. Is the basic study design valid for a randomized controlled trial? 2. Was the study methodologically sound? 3. What are the results? 4. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CONSORT Statement The CONSORT checklist includes 25 items to determine the quality of randomized controlled trials. “Critical appraisal of the quality of clinical trials is possible only if the design, conduct, and analysis of RCTs are thoroughly and accurately described in the report.” 7 more... less... CONSORT (Consolidated Standards of Reporting Trials)
• NHLBI Study Quality Assessment of Controlled Intervention Studies The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. more... less... NHLBI (National Heart, Lung, and Blood Institute)
• JBI Critical Appraisal Tools Checklist for Randomized Controlled Trials JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• ROBINS-I ROBINS-I is a “tool for evaluating risk of bias in estimates of the comparative effectiveness… of interventions from studies that did not use randomization to allocate units… to comparison groups.” 8 more... less... ROBINS-I (Risk Of Bias in Non-randomized Studies – of Interventions)
• NOS This tool is used primarily to evaluate and appraise case-control or cohort studies. more... less... NOS (Newcastle-Ottawa Scale)
• AXIS Cross-sectional studies are frequently used as an evidence base for diagnostic testing, risk factors for disease, and prevalence studies. “The AXIS tool focuses mainly on the presented [study] methods and results.” 9 more... less... AXIS (Appraisal tool for Cross-Sectional Studies)
• NHLBI Study Quality Assessment Tools for Non-Randomized Studies The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. • Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies • Quality Assessment of Case-Control Studies • Quality Assessment Tool for Before-After (Pre-Post) Studies With No Control Group • Quality Assessment Tool for Case Series Studies more... less... NHLBI (National Heart, Lung, and Blood Institute)
• Case Series Studies Quality Appraisal Checklist Developed by the Institute of Health Economics (Canada), the checklist is comprised of 20 questions to assess “the robustness of the evidence of uncontrolled, [case series] studies.” 10
• Methodological Quality and Synthesis of Case Series and Case Reports In this paper, Dr. Murad and colleagues “present a framework for appraisal, synthesis and application of evidence derived from case reports and case series.” 11
• MINORS The MINORS instrument contains 12 items and was developed for evaluating the quality of observational or non-randomized studies. 12 This tool may be of particular interest to researchers who would like to critically appraise surgical studies. more... less... MINORS (Methodological Index for Non-Randomized Studies)
• JBI Critical Appraisal Tools for Non-Randomized Trials JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis. • Checklist for Analytical Cross Sectional Studies • Checklist for Case Control Studies • Checklist for Case Reports • Checklist for Case Series • Checklist for Cohort Studies
• QUADAS-2 The QUADAS-2 tool “is designed to assess the quality of primary diagnostic accuracy studies… [it] consists of 4 key domains that discuss patient selection, index test, reference standard, and flow of patients through the study and timing of the index tests and reference standard.” 13 more... less... QUADAS-2 (a revised tool for the Quality Assessment of Diagnostic Accuracy Studies)
• JBI Critical Appraisal Tools Checklist for Diagnostic Test Accuracy Studies JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• STARD 2015 The authors of the standards note that “[e]ssential elements of [diagnostic accuracy] study methods are often poorly described and sometimes completely omitted, making both critical appraisal and replication difficult, if not impossible.”10 The Standards for the Reporting of Diagnostic Accuracy Studies was developed “to help… improve completeness and transparency in reporting of diagnostic accuracy studies.” 14 more... less... STARD 2015 (Standards for the Reporting of Diagnostic Accuracy Studies)
• CASP Diagnostic Study Checklist This CASP checklist considers various aspects of diagnostic test studies including: 1. Are the results of the study valid? 2. What were the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CEBM Diagnostic Critical Appraisal Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance, and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• SYRCLE’s RoB “[I]mplementation of [SYRCLE’s RoB tool] will facilitate and improve critical appraisal of evidence from animal studies. This may… enhance the efficiency of translating animal research into clinical practice and increase awareness of the necessity of improving the methodological quality of animal studies.” 15 more... less... SYRCLE’s RoB (SYstematic Review Center for Laboratory animal Experimentation’s Risk of Bias)
• ARRIVE 2.0 “The [ARRIVE 2.0] guidelines are a checklist of information to include in a manuscript to ensure that publications [on in vivo animal studies] contain enough information to add to the knowledge base.” 16 more... less... ARRIVE 2.0 (Animal Research: Reporting of In Vivo Experiments)
• Critical Appraisal of Studies Using Laboratory Animal Models This article provides “an approach to critically appraising papers based on the results of laboratory animal experiments,” and discusses various “bias domains” in the literature that critical appraisal can identify. 17
• CEBM Critical Appraisal of Qualitative Studies Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• CASP Qualitative Studies Checklist This CASP checklist considers various aspects of qualitative research studies including: 1. Are the results of the study valid? 2. What were the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• Quality Assessment and Risk of Bias Tool Repository Created by librarians at Duke University, this extensive listing contains over 100 commonly used risk of bias tools that may be sorted by study type.
• Latitudes Network A library of risk of bias tools for use in evidence syntheses that provides selection help and training videos.

References & Recommended Reading

1.     Kolaski, K., Logan, L. R., & Ioannidis, J. P. (2024). Guidance to best tools and practices for systematic reviews .  British Journal of Pharmacology ,  181 (1), 180-210

2.    Portney LG.  Foundations of clinical research : applications to evidence-based practice.  Fourth edition. ed. Philadelphia: F A Davis; 2020.

3.     Fowkes FG, Fulton PM.  Critical appraisal of published research: introductory guidelines.   BMJ (Clinical research ed).  1991;302(6785):1136-1140.

4.     Singh S.  Critical appraisal skills programme.   Journal of Pharmacology and Pharmacotherapeutics.  2013;4(1):76-77.

5.     Shea BJ, Reeves BC, Wells G, et al.  AMSTAR 2: a critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both.   BMJ (Clinical research ed).  2017;358:j4008.

6.     Whiting P, Savovic J, Higgins JPT, et al.  ROBIS: A new tool to assess risk of bias in systematic reviews was developed.   Journal of clinical epidemiology.  2016;69:225-234.

7.     Sterne JAC, Savovic J, Page MJ, et al.  RoB 2: a revised tool for assessing risk of bias in randomised trials.  BMJ (Clinical research ed).  2019;366:l4898.

8.     Moher D, Hopewell S, Schulz KF, et al.  CONSORT 2010 Explanation and Elaboration: Updated guidelines for reporting parallel group randomised trials.  Journal of clinical epidemiology.  2010;63(8):e1-37.

9.     Sterne JA, Hernan MA, Reeves BC, et al.  ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions.  BMJ (Clinical research ed).  2016;355:i4919.

10.     Downes MJ, Brennan ML, Williams HC, Dean RS.  Development of a critical appraisal tool to assess the quality of cross-sectional studies (AXIS).   BMJ open.  2016;6(12):e011458.

11.   Guo B, Moga C, Harstall C, Schopflocher D.  A principal component analysis is conducted for a case series quality appraisal checklist.   Journal of clinical epidemiology.  2016;69:199-207.e192.

12.   Murad MH, Sultan S, Haffar S, Bazerbachi F.  Methodological quality and synthesis of case series and case reports.  BMJ evidence-based medicine.  2018;23(2):60-63.

13.   Slim K, Nini E, Forestier D, Kwiatkowski F, Panis Y, Chipponi J.  Methodological index for non-randomized studies (MINORS): development and validation of a new instrument.   ANZ journal of surgery.  2003;73(9):712-716.

14.   Whiting PF, Rutjes AWS, Westwood ME, et al.  QUADAS-2: a revised tool for the quality assessment of diagnostic accuracy studies.   Annals of internal medicine.  2011;155(8):529-536.

15.   Bossuyt PM, Reitsma JB, Bruns DE, et al.  STARD 2015: an updated list of essential items for reporting diagnostic accuracy studies.   BMJ (Clinical research ed).  2015;351:h5527.

16.   Hooijmans CR, Rovers MM, de Vries RBM, Leenaars M, Ritskes-Hoitinga M, Langendam MW.  SYRCLE's risk of bias tool for animal studies.   BMC medical research methodology.  2014;14:43.

17.   Percie du Sert N, Ahluwalia A, Alam S, et al.  Reporting animal research: Explanation and elaboration for the ARRIVE guidelines 2.0.  PLoS biology.  2020;18(7):e3000411.

18.   O'Connor AM, Sargeant JM.  Critical appraisal of studies using laboratory animal models.   ILAR journal.  2014;55(3):405-417.

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• Dissecting the literature: the importance of critical appraisal

08 Dec 2017

Kirsty Morrison

This post was updated  in 2023.

Critical appraisal is the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context.

Amanda Burls, What is Critical Appraisal?

Why is critical appraisal needed?

Literature searches using databases like Medline or EMBASE often result in an overwhelming volume of results which can vary in quality. Similarly, those who browse medical literature for the purposes of CPD or in response to a clinical query will know that there are vast amounts of content available. Critical appraisal helps to reduce the burden and allow you to focus on articles that are relevant to the research question, and that can reliably support or refute its claims with high-quality evidence, or identify high-level research relevant to your practice.

Critical appraisal allows us to:

• reduce information overload by eliminating irrelevant or weak studies
• identify the most relevant papers
• distinguish evidence from opinion, assumptions, misreporting, and belief
• assess the validity of the study
• assess the usefulness and clinical applicability of the study
• recognise any potential for bias.

Critical appraisal helps to separate what is significant from what is not. One way we use critical appraisal in the Library is to prioritise the most clinically relevant content for our Current Awareness Updates .

How to critically appraise a paper

There are some general rules to help you, including a range of checklists highlighted at the end of this blog. Some key questions to consider when critically appraising a paper:

• Is the study question relevant to my field?
• Does the study add anything new to the evidence in my field?
• What type of research question is being asked? A well-developed research question usually identifies three components: the group or population of patients, the studied parameter (e.g. a therapy or clinical intervention) and outcomes of interest.
• Was the study design appropriate for the research question? You can learn more about different study types and the hierarchy of evidence here .
• Did the methodology address important potential sources of bias? Bias can be attributed to chance (e.g. random error) or to the study methods (systematic bias).
• Was the study performed according to the original protocol? Deviations from the planned protocol can affect the validity or relevance of a study, e.g. a decrease in the studied population over the course of a randomised controlled trial .
• Does the study test a stated hypothesis? Is there a clear statement of what the investigators expect the study to find which can be tested, and confirmed or refuted.
• Were the statistical analyses performed correctly? The approach to dealing with missing data, and the statistical techniques that have been applied should be specified. Original data should be presented clearly so that readers can check the statistical accuracy of the paper.
• Do the data justify the conclusions? Watch out for definite conclusions based on statistically insignificant results, generalised findings from a small sample size, and statistically significant associations being misinterpreted to imply a cause and effect.
• Are there any conflicts of interest? Who has funded the study and can we trust their objectivity? Do the authors have any potential conflicts of interest, and have these been declared?

And an important consideration for surgeons:

• Will the results help me manage my patients?

At the end of the appraisal process you should have a better appreciation of how strong the evidence is, and ultimately whether or not you should apply it to your patients.

Further resources:

• How to Read a Paper by Trisha Greenhalgh
• The Doctor’s Guide to Critical Appraisal by Narinder Kaur Gosall
• CASP checklists
• CEBM Critical Appraisal Tools
• Critical Appraisal: a checklist
• Critical Appraisal of a Journal Article (PDF)
• Introduction to...Critical appraisal of literature
• Reporting guidelines for the main study types

Kirsty Morrison, Information Specialist

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How to Perform a Systematic Literature Review pp 51–68 Cite as

Critical Appraisal: Assessing the Quality of Studies

• Edward Purssell   ORCID: orcid.org/0000-0003-3748-0864 3 &
• Niall McCrae   ORCID: orcid.org/0000-0001-9776-7694 4  
• First Online: 05 August 2020

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There is great variation in the type and quality of research evidence. Having completed your search and assembled your studies, the next step is to critically appraise the studies to ascertain their quality. Ultimately you will be making a judgement about the overall evidence, but that comes later. You will see throughout this chapter that we make a clear differentiation between the individual studies and what we call the body of evidence , which is all of the studies and anything else that we use to answer the question or to make a recommendation. This chapter deals with only the first of these—the individual studies. Critical appraisal, like everything else in systematic literature reviewing, is a scientific exercise that requires individual judgement, and we describe some tools to help you.

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Oxford Centre for Evidence-Based Medicine (OCEBM) (2016) OCEBM levels of evidence. In: CEBM. https://www.cebm.net/2016/05/ocebm-levels-of-evidence/ . Accessed 17 Apr 2020

Aromataris E, Munn Z (eds) (2017) Joanna Briggs Institute reviewer’s manual. The Joanna Briggs Institute, Adelaide

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Daly J, Willis K, Small R et al (2007) A hierarchy of evidence for assessing qualitative health research. J Clin Epidemiol 60:43–49. https://doi.org/10.1016/j.jclinepi.2006.03.014

Article   PubMed   Google Scholar  

EQUATOR Network (2020) What is a reporting guideline?—The EQUATOR Network. https://www.equator-network.org/about-us/what-is-a-reporting-guideline/ . Accessed 7 Mar 2020

Tong A, Sainsbury P, Craig J (2007) Consolidated criteria for reporting qualitative research (COREQ): a 32-item checklist for interviews and focus groups. Int J Qual Health Care 19:349–357. https://doi.org/10.1093/intqhc/mzm042

von Elm E, Altman DG, Egger M et al (2007) The strengthening the reporting of observational studies in epidemiology (STROBE) statement: guidelines for reporting observational studies. PLoS Med 4:e296. https://doi.org/10.1371/journal.pmed.0040296

Article   Google Scholar  

Brouwers MC, Kerkvliet K, Spithoff K, AGREE Next Steps Consortium (2016) The AGREE reporting checklist: a tool to improve reporting of clinical practice guidelines. BMJ 352:i1152. https://doi.org/10.1136/bmj.i1152

Article   PubMed   PubMed Central   Google Scholar  

Moher D, Liberati A, Tetzlaff J et al (2009) Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS Med 6:e1000097. https://doi.org/10.1371/journal.pmed.1000097

Boutron I, Page MJ, Higgins JPT, Altman DG, Lundh A, Hróbjartsson A (2019) Chapter 7: Considering bias and conflicts of interest among the included studies. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (eds). Cochrane Handbook for Systematic Reviews of Interventions version 6.0 (updated July 2019), Cochrane. https://www.training.cochrane.org/handbook

Critical Appraisal Skills Programme (2018) CASP checklists. In: CASP—critical appraisal skills programme. https://casp-uk.net/casp-tools-checklists/ . Accessed 7 Mar 2020

Higgins JPT, Savović J, Page MJ et al (2019) Chapter 8: Assessing risk of bias in a randomized trial. In: Higgins JPT, Thomas J, Chandler J et al (eds) Cochrane handbook for systematic reviews of interventions version 6.0 (updated July 2019). Cochrane, London

Chapter   Google Scholar  

Guyatt GH, Oxman AD, Kunz R et al (2011) GRADE guidelines 6. Rating the quality of evidence—imprecision. J Clin Epidemiol 64:1283–1293. https://doi.org/10.1016/j.jclinepi.2011.01.012

Sterne JAC, Savović J, Page MJ et al (2019) RoB 2: a revised tool for assessing risk of bias in randomised trials. BMJ 366:l4898. https://doi.org/10.1136/bmj.l4898

Sterne JA, Hernán MA, Reeves BC et al (2016) ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions. BMJ 355:i4919. https://doi.org/10.1136/bmj.i4919

Wells GA, Shea B, O’Connell D et al (2019) The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. Ottawa Hospital Research Institute, Ottawa. http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp . Accessed 7 Mar 2020

Cochrane Community (2020) Glossary—Cochrane community. https://community.cochrane.org/glossary#letter-R . Accessed 8 Mar 2020

Messick S (1989) Meaning and values in test validation: the science and ethics of assessment. Educ Res 18:5–11. https://doi.org/10.3102/0013189X018002005

Sparkes AC (2001) Myth 94: qualitative health researchers will agree about validity. Qual Health Res 11:538–552. https://doi.org/10.1177/104973230101100409

Article   CAS   PubMed   Google Scholar  

Aguinis H, Solarino AM (2019) Transparency and replicability in qualitative research: the case of interviews with elite informants. Strat Manag J 40:1291–1315. https://doi.org/10.1002/smj.3015

Lincoln YS, Guba EG (1985) Naturalistic inquiry. Sage Publications, Beverly Hills, CA

Book   Google Scholar  

Hannes K (2011) Chapter 4: Critical appraisal of qualitative research. In: Noyes J, Booth A, Hannes K et al (eds) Supplementary guidance for inclusion of qualitative research in Cochrane systematic reviews of interventions. Cochrane Collaboration Qualitative Methods Group, London

Munn Z, Porritt K, Lockwood C et al (2014) Establishing confidence in the output of qualitative research synthesis: the ConQual approach. BMC Med Res Methodol 14:108. https://doi.org/10.1186/1471-2288-14-108

Toye F, Seers K, Allcock N et al (2013) ‘Trying to pin down jelly’—exploring intuitive processes in quality assessment for meta-ethnography. BMC Med Res Methodol 13:46. https://doi.org/10.1186/1471-2288-13-46

Katikireddi SV, Egan M, Petticrew M (2015) How do systematic reviews incorporate risk of bias assessments into the synthesis of evidence? A methodological study. J Epidemiol Community Health 69:189–195. https://doi.org/10.1136/jech-2014-204711

McKenzie JE, Brennan SE, Ryan RE et al (2019) Chapter 9: Summarizing study characteristics and preparing for synthesis. In: Higgins JPT, Thomas J, Chandler J et al (eds) Cochrane handbook for systematic reviews of interventions version 6.0 (updated July 2019). Cochrane, London

Deeks JJ, Higgins JPT, Altman DG (2019) Chapter 10: Analysing data and undertaking meta-analyses. In: Higgins JPT, Thomas J, Chandler J et al (eds) Cochrane handbook for systematic reviews of interventions version 6.0 (updated July 2019). Cochrane, London

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• Volume 25, Issue 1
• Critical appraisal of qualitative research: necessity, partialities and the issue of bias
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• http://orcid.org/0000-0001-5660-8224 Veronika Williams ,
• Anne-Marie Boylan ,
• http://orcid.org/0000-0003-4597-1276 David Nunan
• Nuffield Department of Primary Care Health Sciences , University of Oxford, Radcliffe Observatory Quarter , Oxford , UK
• Correspondence to Dr Veronika Williams, Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford OX2 6GG, UK; veronika.williams{at}phc.ox.ac.uk

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• qualitative research

Introduction

Qualitative evidence allows researchers to analyse human experience and provides useful exploratory insights into experiential matters and meaning, often explaining the ‘how’ and ‘why’. As we have argued previously 1 , qualitative research has an important place within evidence-based healthcare, contributing to among other things policy on patient safety, 2 prescribing, 3 4 and understanding chronic illness. 5 Equally, it offers additional insight into quantitative studies, explaining contextual factors surrounding a successful intervention or why an intervention might have ‘failed’ or ‘succeeded’ where effect sizes cannot. It is for these reasons that the MRC strongly recommends including qualitative evaluations when developing and evaluating complex interventions. 6

Critical appraisal of qualitative research

Is it necessary.

Although the importance of qualitative research to improve health services and care is now increasingly widely supported (discussed in paper 1), the role of appraising the quality of qualitative health research is still debated. 8 10 Despite a large body of literature focusing on appraisal and rigour, 9 11–15 often referred to as ‘trustworthiness’ 16 in qualitative research, there remains debate about how to —and even whether to—critically appraise qualitative research. 8–10 17–19 However, if we are to make a case for qualitative research as integral to evidence-based healthcare, then any argument to omit a crucial element of evidence-based practice is difficult to justify. That being said, simply applying the standards of rigour used to appraise studies based on the positivist paradigm (Positivism depends on quantifiable observations to test hypotheses and assumes that the researcher is independent of the study. Research situated within a positivist paradigm isbased purely on facts and consider the world to be external and objective and is concerned with validity, reliability and generalisability as measures of rigour.) would be misplaced given the different epistemological underpinnings of the two types of data.

Given its scope and its place within health research, the robust and systematic appraisal of qualitative research to assess its trustworthiness is as paramount to its implementation in clinical practice as any other type of research. It is important to appraise different qualitative studies in relation to the specific methodology used because the methodological approach is linked to the ‘outcome’ of the research (eg, theory development, phenomenological understandings and credibility of findings). Moreover, appraisal needs to go beyond merely describing the specific details of the methods used (eg, how data were collected and analysed), with additional focus needed on the overarching research design and its appropriateness in accordance with the study remit and objectives.

Poorly conducted qualitative research has been described as ‘worthless, becomes fiction and loses its utility’. 20 However, without a deep understanding of concepts of quality in qualitative research or at least an appropriate means to assess its quality, good qualitative research also risks being dismissed, particularly in the context of evidence-based healthcare where end users may not be well versed in this paradigm.

How is appraisal currently performed?

Appraising the quality of qualitative research is not a new concept—there are a number of published appraisal tools, frameworks and checklists in existence. 21–23  An important and often overlooked point is the confusion between tools designed for appraising methodological quality and reporting guidelines designed to assess the quality of methods reporting. An example is the Consolidate Criteria for Reporting Qualitative Research (COREQ) 24 checklist, which was designed to provide standards for authors when reporting qualitative research but is often mistaken for a methods appraisal tool. 10

Broadly speaking there are two types of critical appraisal approaches for qualitative research: checklists and frameworks. Checklists have often been criticised for confusing quality in qualitative research with ‘technical fixes’ 21 25 , resulting in the erroneous prioritisation of particular aspects of methodological processes over others (eg, multiple coding and triangulation). It could be argued that a checklist approach adopts the positivist paradigm, where the focus is on objectively assessing ‘quality’ where the assumptions is that the researcher is independent of the research conducted. This may result in the application of quantitative understandings of bias in order to judge aspects of recruitment, sampling, data collection and analysis in qualitative research papers. One of the most widely used appraisal tools is the Critical Appraisal Skills Programme (CASP) 26 and along with the JBI QARI (Joanna Briggs Institute Qualitative Assessment and Assessment Instrument) 27 presents examples which tend to mimic the quantitative approach to appraisal. The CASP qualitative tool follows that of other CASP appraisal tools for quantitative research designs developed in the 1990s. The similarities are therefore unsurprising given the status of qualitative research at that time.

Frameworks focus on the overarching concepts of quality in qualitative research, including transparency, reflexivity, dependability and transferability (see box 1 ). 11–13 15 16 20 28 However, unless the reader is familiar with these concepts—their meaning and impact, and how to interpret them—they will have difficulty applying them when critically appraising a paper.

The main issue concerning currently available checklist and framework appraisal methods is that they take a broad brush approach to ‘qualitative’ research as whole, with few, if any, sufficiently differentiating between the different methodological approaches (eg, Grounded Theory, Interpretative Phenomenology, Discourse Analysis) nor different methods of data collection (interviewing, focus groups and observations). In this sense, it is akin to taking the entire field of ‘quantitative’ study designs and applying a single method or tool for their quality appraisal. In the case of qualitative research, checklists, therefore, offer only a blunt and arguably ineffective tool and potentially promote an incomplete understanding of good ‘quality’ in qualitative research. Likewise, current framework methods do not take into account how concepts differ in their application across the variety of qualitative approaches and, like checklists, they also do not differentiate between different qualitative methodologies.

On the need for specific appraisal tools

Current approaches to the appraisal of the methodological rigour of the differing types of qualitative research converge towards checklists or frameworks. More importantly, the current tools do not explicitly acknowledge the prejudices that may be present in the different types of qualitative research.

Concepts of rigour or trustworthiness within qualitative research 31

Transferability: the extent to which the presented study allows readers to make connections between the study’s data and wider community settings, ie, transfer conceptual findings to other contexts.

Credibility: extent to which a research account is believable and appropriate, particularly in relation to the stories told by participants and the interpretations made by the researcher.

Reflexivity: refers to the researchers’ engagement of continuous examination and explanation of how they have influenced a research project from choosing a research question to sampling, data collection, analysis and interpretation of data.

Transparency: making explicit the whole research process from sampling strategies, data collection to analysis. The rationale for decisions made is as important as the decisions themselves.

However, we often talk about these concepts in general terms, and it might be helpful to give some explicit examples of how the ‘technical processes’ affect these, for example, partialities related to:

Selection: recruiting participants via gatekeepers, such as healthcare professionals or clinicians, who may select them based on whether they believe them to be ‘good’ participants for interviews/focus groups.

Data collection: poor interview guide with closed questions which encourage yes/no answers and/leading questions.

Reflexivity and transparency: where researchers may focus their analysis on preconceived ideas rather than ground their analysis in the data and do not reflect on the impact of this in a transparent way.

The lack of tailored, method-specific appraisal tools has potentially contributed to the poor uptake and use of qualitative research for informing evidence-based decision making. To improve this situation, we propose the need for more robust quality appraisal tools that explicitly encompass both the core design aspects of all qualitative research (sampling/data collection/analysis) but also considered the specific partialities that can be presented with different methodological approaches. Such tools might draw on the strengths of current frameworks and checklists while providing users with sufficient understanding of concepts of rigour in relation to the different types of qualitative methods. We provide an outline of such tools in the third and final paper in this series.

As qualitative research becomes ever more embedded in health science research, and in order for that research to have better impact on healthcare decisions, we need to rethink critical appraisal and develop tools that allow differentiated evaluations of the myriad of qualitative methodological approaches rather than continuing to treat qualitative research as a single unified approach.

• Williams V ,
• Boylan AM ,
• Lingard L ,
• Orser B , et al
• Brawn R , et al
• Van Royen P ,
• Vermeire E , et al
• Barker M , et al
• McGannon KR
• Dixon-Woods M ,
• Agarwal S , et al
• Greenhalgh T ,
• Dennison L ,
• Morrison L ,
• Conway G , et al
• Barrett M ,
• Mayan M , et al
• Lockwood C ,
• Santiago-Delefosse M ,
• Bruchez C , et al
• Sainsbury P ,
• ↵ CASP (Critical Appraisal Skills Programme). date unknown . http://www.phru.nhs.uk/Pages/PHD/CASP.htm .
• ↵ The Joanna Briggs Institute . JBI QARI Critical appraisal checklist for interpretive & critical research . Adelaide : The Joanna Briggs Institute , 2014 .
• Stephens J ,

Contributors VW and DN: conceived the idea for this article. VW: wrote the first draft. AMB and DN: contributed to the final draft. All authors approve the submitted article.

Competing interests None declared.

Provenance and peer review Not commissioned; externally peer reviewed.

Correction notice This article has been updated since its original publication to include a new reference (reference 1.)

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"Critical appraisal is the process of systematically examining research evidence to assess its validity, results, and relevance before using it to inform a decision."

Hill, A. Spittlehouse, C. What is Critical Appraisal? What is...? series . Retrieved from http://www.whatisseries.co.uk/whatis/pdfs/What_is_crit_appr.pdf

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In cohort studies, groups of individuals, who are initially free of disease, are classified according to exposure or non-exposure to a risk factor and followed over time to determine the incidence of an outcome of interest.  In a prospective cohort study, the exposure information for the study subjects is collected at the start of the study and the new cases of disease are identified from that point on.  In a retrospective cohort study, the exposure status was measured in the past and disease identification has already begun. 

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Studies that start by identifying persons with and without a disease of interest (cases and controls, respectively) and then look back in time to find differences in exposure to risk factors. 

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Studies in which the presence or absence of disease or other health-related variables are determined in each member of a population at one particular time. 

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Critical Appraisal Questionnaires

Critical appraisal is the process of carefully and systematically assessing the outcome of scientific research (evidence) to judge its trustworthiness, value and relevance in a particular context. Critical appraisal looks at the way a study is conducted and examines factors such as internal validity, generalizability and relevance.

Some initial appraisal questions you could ask are:

• Is the evidence from a known, reputable source?
• Has the evidence been evaluated in any way? If so, how and by whom?
• How up-to-date is the evidence?

Second, you could look at the study itself and ask the following general appraisal questions:

• How was the outcome measured?
• Is that a reliable way to measure?
• How large was the effect size?
• What implications does the study have for your practice? Is it relevant?
• Can the results be applied to your organization?

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If you would like to critically appraise a study, we strongly recommend using the app we have developed for iOS and Android:  CAT Manager App

You could also consider using the following appraisal questionnaires (checklists) for specific study designs, but we do not recommend this. 

Appraisal of a meta-analysis or systematic review

Appraisal of a controlled study, appraisal of a cohort or panel study, appraisal of a case control study, appraisal of a cross-sectional study (survey), appraisal of a qualitative study, appraisal of a case study.

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Journalists, researchers and the public often look at society through the lens of generation, using terms like Millennial or Gen Z to describe groups of similarly aged people. This approach can help readers see themselves in the data and assess where we are and where we’re headed as a country.

Pew Research Center has been at the forefront of generational research over the years, telling the story of Millennials as they came of age politically and as they moved more firmly into adult life . In recent years, we’ve also been eager to learn about Gen Z as the leading edge of this generation moves into adulthood.

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Recently, as we were preparing to embark on a major research project related to Gen Z, we decided to take a step back and consider how we can study generations in a way that aligns with our values of accuracy, rigor and providing a foundation of facts that enriches the public dialogue.

A typical generation spans 15 to 18 years. As many critics of generational research point out, there is great diversity of thought, experience and behavior within generations.

We set out on a yearlong process of assessing the landscape of generational research. We spoke with experts from outside Pew Research Center, including those who have been publicly critical of our generational analysis, to get their take on the pros and cons of this type of work. We invested in methodological testing to determine whether we could compare findings from our earlier telephone surveys to the online ones we’re conducting now. And we experimented with higher-level statistical analyses that would allow us to isolate the effect of generation.

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Here’s a short overview of how we’ll approach generational research in the future:

We’ll only do generational analysis when we have historical data that allows us to compare generations at similar stages of life. When comparing generations, it’s crucial to control for age. In other words, researchers need to look at each generation or age cohort at a similar point in the life cycle. (“Age cohort” is a fancy way of referring to a group of people who were born around the same time.)

When doing this kind of research, the question isn’t whether young adults today are different from middle-aged or older adults today. The question is whether young adults today are different from young adults at some specific point in the past.

To answer this question, it’s necessary to have data that’s been collected over a considerable amount of time – think decades. Standard surveys don’t allow for this type of analysis. We can look at differences across age groups, but we can’t compare age groups over time.

Another complication is that the surveys we conducted 20 or 30 years ago aren’t usually comparable enough to the surveys we’re doing today. Our earlier surveys were done over the phone, and we’ve since transitioned to our nationally representative online survey panel , the American Trends Panel . Our internal testing showed that on many topics, respondents answer questions differently depending on the way they’re being interviewed. So we can’t use most of our surveys from the late 1980s and early 2000s to compare Gen Z with Millennials and Gen Xers at a similar stage of life.

This means that most generational analysis we do will use datasets that have employed similar methodologies over a long period of time, such as surveys from the U.S. Census Bureau. A good example is our 2020 report on Millennial families , which used census data going back to the late 1960s. The report showed that Millennials are marrying and forming families at a much different pace than the generations that came before them.

Even when we have historical data, we will attempt to control for other factors beyond age in making generational comparisons. If we accept that there are real differences across generations, we’re basically saying that people who were born around the same time share certain attitudes or beliefs – and that their views have been influenced by external forces that uniquely shaped them during their formative years. Those forces may have been social changes, economic circumstances, technological advances or political movements.

When we see that younger adults have different views than their older counterparts, it may be driven by their demographic traits rather than the fact that they belong to a particular generation.

The tricky part is isolating those forces from events or circumstances that have affected all age groups, not just one generation. These are often called “period effects.” An example of a period effect is the Watergate scandal, which drove down trust in government among all age groups. Differences in trust across age groups in the wake of Watergate shouldn’t be attributed to the outsize impact that event had on one age group or another, because the change occurred across the board.

Changing demographics also may play a role in patterns that might at first seem like generational differences. We know that the United States has become more racially and ethnically diverse in recent decades, and that race and ethnicity are linked with certain key social and political views. When we see that younger adults have different views than their older counterparts, it may be driven by their demographic traits rather than the fact that they belong to a particular generation.

Controlling for these factors can involve complicated statistical analysis that helps determine whether the differences we see across age groups are indeed due to generation or not. This additional step adds rigor to the process. Unfortunately, it’s often absent from current discussions about Gen Z, Millennials and other generations.

When we can’t do generational analysis, we still see value in looking at differences by age and will do so where it makes sense. Age is one of the most common predictors of differences in attitudes and behaviors. And even if age gaps aren’t rooted in generational differences, they can still be illuminating. They help us understand how people across the age spectrum are responding to key trends, technological breakthroughs and historical events.

Each stage of life comes with a unique set of experiences. Young adults are often at the leading edge of changing attitudes on emerging social trends. Take views on same-sex marriage , for example, or attitudes about gender identity .

Many middle-aged adults, in turn, face the challenge of raising children while also providing care and support to their aging parents. And older adults have their own obstacles and opportunities. All of these stories – rooted in the life cycle, not in generations – are important and compelling, and we can tell them by analyzing our surveys at any given point in time.

When we do have the data to study groups of similarly aged people over time, we won’t always default to using the standard generational definitions and labels. While generational labels are simple and catchy, there are other ways to analyze age cohorts. For example, some observers have suggested grouping people by the decade in which they were born. This would create narrower cohorts in which the members may share more in common. People could also be grouped relative to their age during key historical events (such as the Great Recession or the COVID-19 pandemic) or technological innovations (like the invention of the iPhone).

By choosing not to use the standard generational labels when they’re not appropriate, we can avoid reinforcing harmful stereotypes or oversimplifying people’s complex lived experiences.

Existing generational definitions also may be too broad and arbitrary to capture differences that exist among narrower cohorts. A typical generation spans 15 to 18 years. As many critics of generational research point out, there is great diversity of thought, experience and behavior within generations. The key is to pick a lens that’s most appropriate for the research question that’s being studied. If we’re looking at political views and how they’ve shifted over time, for example, we might group people together according to the first presidential election in which they were eligible to vote.

With these considerations in mind, our audiences should not expect to see a lot of new research coming out of Pew Research Center that uses the generational lens. We’ll only talk about generations when it adds value, advances important national debates and highlights meaningful societal trends.

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