Emergence of Large Treatment Effects From Small Trials

摘要

To the Editor: After analyzing forest plots from the Coch-rane Database of Systematic Reviews, Dr Pereira and colleagues reported that most large treatment effects emerged from small trials. This finding mirrors what epidemiologists and medical statisticians have known for years: large treatment effects appear in most meta-analyses as asymmetry in the scatter of points on funnel plots of effect magnitude against standard error.