Useful concepts for critical appraisal: 1. study design

Critical appraisal is the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context.¹ Critical appraisal skills can be applied to almost any published research study. There are many resources available to assist with critical appraisal including a variety of checklists. However, for a checklist to be effective, one has to have a good understanding of the points to be considered. Therefore, an understanding of the research process, the rationale, strengths and weaknesses of different study designs and statistical and clinical inference are all essential to enable the reader to appraise effectively.

Scientific research usually involves undertaking a methodological study in order to answer a specific question. The introduction of a study should ideally summarize the literature, highlighting any shortcomings and clearly defining the questions that the study is intending to answer (its aims). These may include a hypothesis that will be tested, such as whether a treatment is effective (Box 1).