6. How do I know if the evidence is good enough?

Appraising the quality of a piece of evidence is a crucial step in making an evidence-based decision. There are lots of tools for helping you consider the quality of evidence.

Some of the best known and widely used are produced by the Critical Appraisal Skills Programme (CASP) based in Oxford, UK. These tools or checklists vary according to the type of evidence you are appraising. See the checklist for qualitative research, or quantitative research such as a randomised controlled trial, or secondary evidence such as a systematic review. Other tools can be found by searching for ‘critical appraisal tools’ online. There is a similar process for appraising a piece of grey literature.

If you would like further guidance about how to carry out a critical appraisal of a piece of health evidence, here is a range of useful resources:

• Aimed at the complete beginner, this short workbook produced by UWE Bristol takes you through the process of appraising health information
• A learning resource from the University of Manchester explaining more about critical appraisal, different types of study design and what to look for
• An interactive tool produced by the University of Glasgow, that guides you through a series of appraisal questions to help you interpret a published health research article