Objective: the Cochrane Statistical Methods Group has developed a series of workshops addressing statistical guidelines as formulated in the Cochrane Handbook for Systematic Reviews of Interventions. This workshop will provide review authors with the knowledge to understand and investigate variability across studies in a meta-analysis and to recognize the limitations of the methods available.

Description: this training workshop will address approaches to dealing with between-study variability or heterogeneity in the results of a series of clinical trials. We will first discuss some potential sources of between-study variability and provide an overview of methods for identifying whether heterogeneity poses a problem in a particular set of studies. We then will focus on issues related to dealing with study variability once it has been identified. In particular, we will discuss the decision on whether or not to combine results; the choice between fixed-effect and random-effects analyses; and the use of subgroup analyses (with a brief mention of meta-regression). Discussion will be supplemented with practical examples from the Cochrane Database of Systematic Reviews.