In statistics, a<unk>  combines the results of several studies that address a set of related research hypotheses. The first<unk>  was performed by Karl Pearson in 1904, in an attempt to overcome the problem of reduced statistical power in studies with small sample sizes; analyzing the results from a group of studies can allow more accurate data analysis.
Although<unk>  is widely used in epidemiology and evidence-based medicine today, a<unk>  of a medical treatment was not published until 1955. In the 1970s, more sophisticated analytical techniques were introduced in educational research, starting with the work of Gene V. Glass, Frank L. Schmidt, and John E. Hunter.
The online Oxford English Dictionary lists the first usage of the term in the statistical sense as 1976 by Glass. The statistical theory surrounding<unk>  was greatly advanced by the work of Nambury S. Raju, Larry V. Hedges, Ingram Olkin, John E. Hunter, and Frank L. Schmidt.
Meta-analysis
Systematic review
Cohort study
Longitudinal study
Block design
Agent study
Action study
Survival analysis