2. A sociologist conducted a study of divorce patterns in a Midwestern city. In the study, 200 divorced people were selected at random, and X, the number of years married before divorce, was measured. From this sample, it was found that the sample mean was 8.7 years, and that sx = 3.6 years.

(a) Construct an 80% confidence interval on the average length of marriage before divorce.
(b) Construct a 50% confidence interval on the average length of marriage before divorce.

Use the previously indicated table to find Z values ± 40% from mean (a) and ± 25% from mean (b).

Confidence interval = mean ± ? SEm

SEm = SD/√(n-1)