ABSTRACT
Meta-analysis refers to a collection of methods for combining quantitative information from several sources to give a summary statistic together with its uncertainties. The results strengthen our knowledge beyond that contributed even by multiple single studies and may guide diagnosis and treatment of patients and point toward future research.
We illustrate the variety of topics, methods, and statistical techniques through closer scrutiny of a few meta-analyses published during 1989. The many statistical methods for combining data take different forms, and they are based upon different assumptions. We explain the importance, and review the reporting, of eight attributes of meta-analysis: methods of searching, ehgibility criteria, number of articles, outcome variables, study design, results used for combining, homogeneity, and statistical methods. These items may help the reader evaluate a meta-analysis.
