A comparison of the mean scores of two groups on a test yields an effect size (ES) of 1.41. An ES of this magnitude means that
A) the difference between the mean scores of the two groups is trivial.
B) the difference between the mean scores of the two groups is large.
C) the difference between the standard deviations of the two groups is trivial.
D) both a and c above are correct.

Question

Quizplus · Accepted Answer

An effect size (ES) of 1.41 indicates a large difference between the mean scores of the two groups, suggesting a significant impact or difference in the performance or characteristics measured by the test. Effect size is a quantitative measure of the magnitude of the experimenter effect. The conventions for interpreting effect sizes consider values around 0.2 to be small, around 0.5 to be medium, and values of 0.8 or above to be large. Therefore, an ES of 1.41 is considered large.

A Comparison of the Mean Scores of Two Groups on a Test