Statistical Proof in Inconclusive 'Negative' Trials

Abstract

Three hundred thirty-five published articles from six medical journals that contained "negative" results were examined to determine the probability of detecting "small," "medium," and "large" therapeutic improvements. The mean probability of detecting a small effect size was.138; for a medium effect size, the probability was.387; and for a large effect size, it was.614. (<i>Arch Intern Med</i>1981;141-1307-1310)