Calculate Cohen's d for t = 2.45 with N = 40 for each of the two groups.

A) .06
B) .28
C) .55
D) .79

To calculate Cohen's d we need to divide the difference between the means by the pooled standard deviation. Without the means and standard deviations reported, we cannot calculate it directly. However, we can estimate the effect size using online calculators or reference tables based on the t-value and sample size. For t = 2.45 and N1 = N2 = 40, Cohen's d is approximately 0.55, which corresponds to a moderate effect size. Option C is the closest choice, whereas options A and B represent small effect sizes, and option D represents a large effect size, which is unlikely to be the case with a t-value of 2.45.