This lecture includes these contents: Meta analysis, a review of literature, function of meta analysis, the historical background, fixed effect model,. Invite you to consult this lecture. | Meta-analysis The EBM workshop , MD; PhD of Epidemiology Ahaghdoost@ EBM workshop Meta analysis Definition Meta-analysis: a type of systemic review that uses statistical techniques to quantitatively combine and summarize results of previous research A review of literature is a meta-analytic review only if it includes quantitative estimation of the magnitude of the effect and its uncertainty (confidence limits). EBM workshop Meta analysis Function of Meta-Analysis(1) 1-Identify heterogeneity in effects among multiple studies and, where appropriate, provide summary measure 2-Increase statistical power and precision to detect an effect 3-Develop ,refine, and test hypothesis continued EBM workshop Meta analysis Function of Meta-Analysis(2) continuation 4-Reduce the subjectivity of study comparisons by using systematic and explicit comparison procedure 5-Identify data gap in the knowledge base and suggest direction for future research 6-Calculate sample size for . | Meta-analysis The EBM workshop , MD; PhD of Epidemiology Ahaghdoost@ EBM workshop Meta analysis Definition Meta-analysis: a type of systemic review that uses statistical techniques to quantitatively combine and summarize results of previous research A review of literature is a meta-analytic review only if it includes quantitative estimation of the magnitude of the effect and its uncertainty (confidence limits). EBM workshop Meta analysis Function of Meta-Analysis(1) 1-Identify heterogeneity in effects among multiple studies and, where appropriate, provide summary measure 2-Increase statistical power and precision to detect an effect 3-Develop ,refine, and test hypothesis continued EBM workshop Meta analysis Function of Meta-Analysis(2) continuation 4-Reduce the subjectivity of study comparisons by using systematic and explicit comparison procedure 5-Identify data gap in the knowledge base and suggest direction for future research 6-Calculate sample size for future studies EBM workshop Meta analysis Historical background Ideas behind meta-analysis predate Glass’ work by several decades R. A. Fisher (1944) “When a number of quite independent tests of significance have been made, it sometimes happens that although few or none can be claimed individually as significant, yet the aggregate gives an impression that the probabilities are on the whole lower than would often have been obtained by chance” (p. 99). Source of the idea of cumulating probability values W. G. Cochran (1953) Discusses a method of averaging means across independent studies Laid-out much of the statistical foundation that modern meta-analysis is built upon (., inverse variance weighting and homogeneity testing) EBM workshop Meta analysis Basic concepts The main outcome is the overall magnitude of the effect. It's not a simple average of the magnitude in all the studies. Meta-analysis gives more weight to studies with more precise estimates. The weighting factor is 1/(standard
