Inferences About a Quantile Shift Measure of Effect Size When There Is a Covariate

When comparing two independent groups, a possible appeal of the quantile shift measure of effect size is that its magnitude takes into account situations where one or both distributions are skewed. Extant results indicate that a percentile bootstrap method performs reasonably well given the goal of making inferences about this measure of effect size. The goal here is to suggest a method for making inferences about this measure of effect size when there is a covariate. The method is illustrated with data dealing with the wellbeing of older adults.