A one-sample t test was conducted which resulted in a significant effect. The sample mean was 95 based on a sample size of n = 25. The population mean was 90 with an estimated standard deviation of 8.42. What was Cohen's d effect size?
A) 2.98
B) -2.98
C) +.59
D) -.59

Question

Quizplus · Accepted Answer

Cohen's d effect size can be calculated using the following formula:

d = (sample mean - population mean) / estimated standard deviation

Substituting the values:

d = (95 - 90) / 8.42 
d = 0.59

Since the sample mean is larger than the population mean, the effect size is positive. The correct answer is C, +0.59.

A One-Sample T Test Was Conducted Which Resulted in a Significant