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Monthly Archives: December 2017

The Logic Behind Meta-analysis – Random-effects Model


The fixed model starts with the assumption that true effect size is the same in all studies. However, in many systematic reviews this assumption is implausible. When we decide to incorporate a group of studies in a meta-analysis, we assume that the studies have enough in common that it makes sense to synthesize the information, […]

The Logic Behind Meta-analysis – Fixed-ffect Model


Effect Size (Based on Means) When the studies report means and standard deviations (more precisely, the sample standard error of the mean), the preferred effect size is usually the raw mean difference, the standardized mean difference mean difference, or the response ratio. When the outcome is reported on a meaningful scale and all studies in […]