The leader of two postpartum women's support groups is interested in the depression levels of the women in her groups. She administers the Center for Epidemiologic Studies Depression Scale (CES-D) screening test to the members of her groups. The CES-D is a 20-question self-test that measures depressive feelings and behaviors during the previous week. The mean depression level from the screening test for the 6 women in the first group is μ1=15; the mean depression level for the 12 women in the second group is μ2= 12.

Without calculating the weighted mean for the combined group, you know that the weighted mean is:
a. Midway between 15 and 12
b. Closer to 15 than to 12
c. Closer to 12 than to 15

Compute the weighted mean.

The support group leader realizes that she should also screen for alcohol abuse, so she gives the women in her two groups the Michigan Alcohol Screening Test (MAST). The MAST is a 22-question self-test focusing on the use and abuse of alcohol. The first group has a mean score of μ1= 18. The second group has a mean score of μ2= 12.

Compute the weighted mean.