(Essay found in Nesselroade & Grimm, 2019; pg. 355) Using the 1960 volume of the Journal of Abnormal and Social Psychology, Cohen (1962) conducted an interesting study. Although the authors of the articles in that volume did not use power analyses, Cohen computed the power of the statistical tests used in each of the studies. According to Cohen’s early guidelines, a small effect size is about 0.20; a medium effect size is around 0.50; and a large effect size is around 0.80. Assuming that the researchers would want to detect a medium treatment-effect size, the average power of the tests