The combination of studies is described, with particular attention to the objectives, databases, methods, and results of a combination. Two fallacies in the use of p-values as the sole summaries of studies are described. Four examples are discussed: (1) an overview of trials of some new formulations of a drug; (2) an overview of the effects of placebo; (3) the discovery of argon; and (4) an overview of fibrinolytic therapy. In conclusion, recommendations are made concerning the combination of studies.
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