A researcher was interested in assessing gender and response to pain, so conducted a t-test. The mean for males was 66.25 and the mean for females was 78.24, with both groups having a standard deviation of 7. What is the effect size using Cohen's d?
A) -1.712
B) 1.7
C) 0
D) 1.712

Question

Quizplus · Accepted Answer

Cohen's d = (mean difference) / (pooled standard deviation)
mean difference = 78.24 - 66.25 = 11.99
pooled standard deviation = sqrt(((n1-1) * s1^2 + (n2-1) * s2^2) / (n1 + n2 - 2))
= sqrt(((49-1) * 7^2 + (49-1) * 7^2) / (49 + 49 - 2))
= sqrt(2*48*49/96) = 7.00
Cohen's d = 11.99 / 7 = 1.712. 
Therefore, the answer is D.

A Researcher Was Interested in Assessing Gender and Response to Pain