Meta-analysis at middle age: a personal history

Abstract

The 40-year history of meta-analysis is traced from the vantage point of one of its originators. Research syntheses leading to the first examples of meta-analysis are identified. Early meta-analyses of the literature on psychotherapy outcomes and school class size are recounted. The influence on the development of meta-analysis of several statisticians and psychologists is described. Finally, some directions for future development of research synthesis methods are suggested.

Keywords: meta-analysis; psychotherapy; research synthesis.