# Answers to the ES Questions

 d = M1 - M2 / �[(s1�+ s2�) / 2]    = D = 7.50 - 2.725 / �[(2.038�+ 2.592�) / 2]    = 2.05 Cohen's d Compute Cohen's d using the two standard deviations. How large is the d using Cohen's interpretation of effect sizes? d = 2t/�(df)    = 2(9.16)�73.89    = 2.13 Cohen's d Compute Cohen's d using the value of the t-test statistic. Are the two values of d similar? g = 2t / �N    = 2(9.16) / �80    = 2.05 Hedges's g Compute Hedges's g using the t-test statistic. ```D = M1 - M2 / s ``` control ```  = 7.50 - 2.725 / 2.038 = 2.34 ``` Glass's delta Calculate Glass's delta using the standard deviation of the control group. rYl = �[t� / (t� + df)]       = �[9.16� / (9.16� + 73.89)]      = .73 Effect size correlation The effect size correlation was computed by SPSS as the correlation between the iv (TREATGRP) and the dv (SUDS4), rY>l = . Calculate the effect size correlation using the t value. rYl = d / �(d� + 4)      = 2.05 / �(2.05� + 4)      = .72 Effect size correlation Use Cohen's d to calculate the effect size correlation.