Cohen's d Effect Size Calculator: Example & Interpretation

To calculate the size of Cohen's d, we need the means and standard deviations of both groups.

For the treatment group: Mean (M) = 10 Standard Deviation (SD) = 2

For the control group: Mean (M) = 8 Standard Deviation (SD) = 2

To calculate Cohen's d, we use the formula: d = (M1 - M2) / SD

d = (10 - 8) / 2 = 2 / 2 = 1

The size of Cohen's d is 1, which is considered large.