Estimating required information size and quantifying diversity in a metaanalysis.
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Jesper Brok, Copenhagen Trial Unit
Christian Gluud, Copenhagen Trial Unit
Kristian Thorlund, Copenhagen trial
*Jørn Wetterslev, Copenhagen Trial Unit
Keywords: metaanalysis, heterogeneity, sample size
There is increased awareness that metaanalyses need to attain an information size to detect or reject an anticipated intervention effect. Information size calculations need to consider the total variability in a metaanalysis to preserve the desired error rates. We derive a correction factor that readily yields the expression for the required information size under any metaanalysis model. We also obtain a central measure of diversity in a metaanalysis, defined as the percentage of total variance reduction when the model of pooling is changed from a randomeffects model to a fixedeffect model. We show that this measure is an unbiased quantification of the percentage of variation due to intertrial variability rather than sampling error in a metaanalysis.We prove that diversity is greater than heterogeneity in all randomeffects models. The properties and capabilities of diversity and the traditional measure for heterogeneity are illustrated in 7 metaanalysis
