# Calculating Cohen's d Step-by-Step Cohen's d is a measure of **effect size** indicating the standardized difference between two means. The formula is: \[ d = \frac{M_1 - M_2}{SD_{pooled}} \] Where: - \( M_1 \) = Mean of group 1 - \( M_2 \) = Mean of group 2 - \( SD_{pooled} \) = Pooled standard deviation --- ## Step 1: Identify Values Given: - \( M_1 = 145 \) - \( M_2 = 115 \) - \( SD_{pooled} = 30 \) --- ## Step 2: Calculate Mean Difference \[ M_1 - M_2 = 145 - 115 = 30 \] --- ## Step 3: Plug Values into Formula \[ d = \frac{30}{30} \] --- ## Step 4: Calculate Cohen's d \[ d = 1. \] --- ## Final Answer **Cohen's d = 1.** This indicates a large effect size (a difference of one pooled standard deviation between the two group means).