Answers to the ES Questions
ANSWERS TO ES
Answers to the ES Questions
d = M_{1}  M_{2} / �[(s_{1}�+ s_{2}�) / 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 
d = 2t/�(df) = 2(9.16)�73.89 = 2.13 
Cohen's d
Compute Cohen's d using the value of the ttest 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 ttest statistic. 
D = M_{1}  M_{2} / 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. 
r_{Y}_{l }= �[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), r_{Y}>_{l }= . Calculate the effect size correlation using the t value. 
r_{Y}_{l }= d / �(d� + 4) = 2.05 / �(2.05� + 4) = .72 
Effect size correlation
Use Cohen's d to calculate the effect size correlation. 