APPRAISE the evidence for its validity (closeness to the truth), impact and applicability (usefulness in clinical practice)
"By asking the question ‘What are the strengths and weaknesses of this literature?’ you will determine the quality of the literature you have and whether it is of high enough quality to include in your review and, if so, what weight it should have in answering your question. This process is generally referred to as ‘critical appraisal’." Aveyard, H., (2014). Doing a literature review in health and social care : A practical guide (3rd ed.). Open University Press, p. 103.
A critical step in Evidence Based Practice is to appraise the evidence that you have located from your search of the literature. Each study that you plan to include in your literature review or evidence synthesis should be evaluated in terms of its validity, risk of bias and applicability to your clinical setting.
The aim of critical appraisal is to determine the strength of evidence of individual studies and to evaluate the generalisability of the studies' results.
The videos and links to resources on this page will help you conduct critical appraisals of published literature.
Cochrane Common Mental Disorders. (2019, March 29). Introduction to critical appraisal [streaming video]. https://www.youtube.com/watch?v=H8Y-yfi3vp4&t=18s
The first in a series of seven videos that provide a step by step introduction to critical appraisal of research. In the first video the fundamental concepts of critical appraisal are explained, validity, trustworthiness of results, value and relevance. Each of the videos in the series explores a research design and applies the CASP tool in conducting a critical appraisal. Click on the links below to view the videos in this series.
Critical appraisal using the CASP tool to specific study designs - click on the links below for an explanation of the different study designs and examples of the critical appraisal process.
Systematic Reviews and meta-analysis - applying the CASP checklist
Randomized controlled trials applying - the CASP checklist
Observational studies : Cohort Studies - applying the CASP checklist
Observational studies: Case control studies - applying the CASP checklist
Observational studies: Cross sectional studies
Diagnostic Studies - applying the CASP checklist
The tools used for critically appraising the literature and the criteria you use to appraise an individual study will be determined by the type of studies you have included in your literature review.
There are numerous checklists available to guide you in appraising the literature. Remember to select the checklist that matches each individual journal articles study design.
CASP Critical Assessment Skills Programme checklists. There are eight critical appraisal tools designed for use with Systematic Reviews, Randomised Controlled Trials, Cohort Studies, Case Control Studies, Economic Evaluations, Diagnostic Studies, Qualitative studies and Clinical Prediction Rule.
JBI’s Critical Appraisal Tools. There are thirteen checklists designed to assist in assessing the trustworthiness, relevance and results of published papers. Checklists for critical appraisal of RCT's, systematic reviews and qualitative research are included here.
Centre for Evidence-Based Medicine Critical appraisal worksheets from the CEBM, Oxford University. Includes worksheets to use for critical appraisal of systematic reviews, RCTs, prognosis studies, diagnostic studies and qualitative studies.
This video from ISU libraries provides a clear overview of the critical appraisal process as well as an example of using a matrix to synthesise evidence in a literature review.
When appraising quantitative study designs it is helpful to have an understanding of the statistics used to explain the findings. The links below are to websites, videos and books that provide an explanation of some of the statistical processes and terms you will come across when reading the health literature.
Encyclopedia of Research Design by
From A-to-Z, this work covers the spectrum of research design strategies and topics including, among other things: fundamental research design principles, ethics in the research process, quantitative versus qualitative and mixed-method designs, completely randomized designs, multiple comparison tests, diagnosing agreement between data and models, fundamental assumptions in analysis of variance, factorial treatment designs, complete and incomplete block designs, Latin square and related designs, hierarchical designs, response surface designs, split-plot designs, repeated measures designs, crossover designs, analysis of covariance, statistical software packages, and much more.