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Studies that are used in a review are described in a standardised way that is suitable for each review. The detail provided facilitates transparency in how each study contributes to the overall findings of the review, and the overall reliabillity of the review.
There are three key reasons for describing (or coding) the studies in a systematic review.
The EPPI-Centre coding guidelines in education:
Critical appraisal involves checking the quality, reliability and relevance of the studies in the review in relation to the review question. It appraises each study in terms of the following aspects:.
In addition, the studies are collectively appraised in terms of how they support the review findings and evidence claims of the review. For example, if the research evidence comprises of studies that have wide variation of findings, this reduces the strength of the evidence claims.
There are many standardised tools available for critical appraisal depending on the study design and the type of review. The approach to critical appraisal and the appraisal decisions for each study should be reported.
Commonly-used tools for appraising research evidence in reviews:
It is important for users of systematic reviews to consider the quality of the whole review. There are three separate elements that contribute an appraisal:
There are tools to help with the appraisal of a whole review. Some of these are specific to certain types of reviews, and others are more generic.
Some tools focus only on appraising the methods of specific types of reviews: