Evidence-Based Medicine: Review and Practice: Appraise: Identifying the best evidence

Evidence hierarchies are a tool for quick appraisal of search results. They help you filter your searches to articles that are most likely the best* evidence for the kind of question you are asking.

*Remember that all evidence must be critically appraised. A poorly-conducted or -reported randomized trial does not provide stronger evidence than the results of a well-conducted cohort study.