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
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).