Summary
Cohen’s d is one of the most popular measures of the effect size. Unfortunately, it was designed for the normal distribution, which may make it a misleading measure in the non-normal case. And the real distributions are never normal. When we discuss deviations from normality, we should treat the illusion of normality not as an atomic mental construction, but rather as a set of independent assumptions, each of which may be violated independently. In this post, I take a look at what kind of issues...