If an experimental group's mean of 20 indicates fewer undesirable symptoms than the control group's mean of 25,and the standard deviation is 10,then the Cohen's d effect size should be reported as:
A)+ .50
B)- .50
C)+5.0
D)-5.0

Question

Quizplus · Accepted Answer

Cohen's d effect size is calculated by subtracting the mean of the control group from the mean of the experimental group, and then dividing the result by the standard deviation. In this case, the mean difference is (20-25) = -5, and the standard deviation is 10.

Therefore, Cohen's d = -5/10 = -0.5.

However, since the question asks for the absolute value of Cohen's d (i.e., the magnitude of the effect size), we should report it as +0.5.

If an Experimental Group's Mean of 20 Indicates Fewer Undesirable