ArchiveJanuary 2014

Why Cohen’s effect size rule should be avoided

From Durlak (2009), How to select, calculate, and interpret effect sizes: Many authors still routinely refer to Cohen’s (1988) comments made in reference to power analysis that SMDs of 0.20 are “small” in magnitude, those around 0.50 are “medium” and those around or above 0.80 are “large.” In terms of r, Cohen suggested corresponding figures of 0.10, 0.30, and 0.50. What many researchers do...

About me


Professor and quant guy. Libertarian turned populist Republican. Trying to learn Japanese and play Spanish Baroque music on the ukulele.

Subscribe via email

Enter your email address to subscribe to my blog and receive notifications of new posts by email.