- (written as Meta-analysis)
A statistical method of integrating quantitative research results from several research studies. 'Meta-' has a Greek origin and indicates, amongst other things, that the subject matter (in this case 'analysis') has a second-order character: an analysis of analyses. A meta-analysis is a form of systematic review of literature in which the quantitative results of several studies are systematically combined to generate more precise estimates of the effects under investigation, improve on the power of individual studies to detect effects, and to raise and discuss matters that may not have been evident in the individual studies. Meta-analysis cannot correct for any defects that run throughout a literature (for example, the use of the potentially less valid outcome 'change in tumour size' rather than 'postponed death' as the socially relevant outcome of a screening programme).
Meta-analysis has several advantages over traditional narrative re- views. It is relatively free of the subjectivity in personally selected samples. It not only shows the direction of the effect (up or down), it also quantifies it and identifies the determining variables. It should include all the quantitative empirical studies relevant to the research question. The criteria used for selecting the studies included in the review are explicitly stated. Meta-analyses are usually presented in the form of a forest plot.