Andrea is told that the means of two groups in a study were statistically significant. She knows the means and standard deviations of the two groups and is interested in calculating an estimate of effect size. Given this information, which effect size estimate should she calculate?
A)F
B)Effect size r
C)Cohen's d
D)Alpha

Question

Quizplus · Accepted Answer

Cohen's d is the most appropriate effect size estimate to use in this situation when comparing means of two groups with known standard deviations. It is calculated by dividing the difference between the means by the pooled standard deviation of the two groups. This measure allows for the comparison of effect size across studies and provides a standardized measure of the magnitude of the difference between the two groups. F is not an appropriate effect size estimate in this situation, as it is used for comparing variances in ANOVA tests. Effect size r is used for correlational studies. Alpha is a significance level used in hypothesis testing to determine the probability of rejecting the null hypothesis when it is true, it is not an effect size estimate.

Andrea Is Told That the Means of Two Groups in a Study