Introduction

Meta-analysis is a set of statistical procedures designed to accumulate experimental and correlational results across independent studies that address a related set of research questions. Unlike traditional research methods, meta-analysis uses the summary statistics from individual studies as the data points. A key assumption of this analysis is that each study provides a differing estimate of the underlying relationship within the population (rho). By accumulating results across studies, one can gain a more accurate representation of the population relationship than is provided by the individual study estimators.

While there are a variety of other meta-analysis techniques, this paper will focus on the methods developed by Hunter and Schmidt (Hunter, Schmidt and Jackson, 1982, Hunter and Schmidt, 1990).

Glass and colleagues (e.g., Glass, 1976; 1977; Glass &;Smith, 1977; McGaw &;Glass, 1980; Smith &;Glass, 1977; and Smith, Glass &;Miller, 1980) coined the term meta-analysis, and introduced most of the currently used procedures to psychology.

Meta-analysis refers to the analysis of analyses . . . the statistical analysis of a large collection of analysis results from individual studies for the purpose of integrating the findings. It connotes a rigorous alternative to the casual, narrative discussions of research studies which typify our attempts to make sense of the rapidly expanding research literature.

(Glass, 1976, p 3).