11. Paired Comparisons of Means. A family counseling service offers a 1-day program of training in meal planning which they claim is effective in reducing cholesterol levels of individuals completing the course. In order to assess the effectiveness of the program, a consumer advocacy group randomly samples the cholesterol levels of 50 program participants both one day before and one month after the course is taken. They then summarize the pairs of observations on the individuals by reporting the sample mean and sample standard deviation of the differences between the before and after observations of the 50 program participants. Their finding were d ¼ 11.73 and s ¼ 3.89.