Evaluating Results Using Corrected and Uncorrected Effect Size Estimates

Abstract

Magnitude-of-effect (ME) statistics, when adequately understood and correctly used, are important aids for researchers who do not want to place a sole reliance on tests of statistical significance in substantive result interpretation. We describe why methodologists encourage the use of ME indices as interpretation aids and discuss different types of ME estimates. We discuss correction formulas developed to attenuate statistical bias in ME estimates and illustrate the effect these formulas have on different sample and effect sizes. Finally, we discuss several cautions against the indiscriminate use of these statistics and offer reasons why ME statistics, like all substantive result interpretation aids, are useful only when their strengths and limitations are understood by researchers.