Researchers also considered effect size between groups and reported both d and the distribution overlap
(Cohen,1988; Valentine & Cooper, 2003). The distribution overlap expresses what percentage of scores in the group with a lower mean are surpassed by the average score of the group with a higher mean score; it also indicates what the percentile standing of one group’s mean score is relative to another’s mean score (Carson, n.d.; Valentine & Cooper, 2003).
This measure is perhaps more useful than reporting only the broad guidelines of small, medium, and large effect sizes
(Cohen,1988).