An introduction to meta-analysis for psychotherapy outcome research.

Meta-analysis consists of a set of statistical techniques for quantitatively aggregating and summarizing the results of several studies. This article provides an introductory tutorial to the process of meta-analysis for psychotherapy outcome research, including identifying and collecting studies, coding effect sizes, coding substantive and methodological information, combining effect sizes, interpreting effect sizes, and conducting moderator and sensitivity analyses. To assist readers new to meta-analysis, the parallels between the process of primary research and the process of meta-analysis are highlighted. Software for conducting meta-analytic research is briefly discussed.