The U. S. Census Bureau collects data on the ages of married people. Suppose that eight married couples are randomly selected and have the ages given in the following table. Determine the 95%
95
%
confidence interval for the true mean difference between the ages of married males and married females.

Let d=(age of husband)−(age of wife)
d
=
(age of husband)
−
(age of wife)
. Assume that the ages are normally distributed for the populations of both husbands and wives in the U. S.

Husband 68
68
52
52
54
54
49
49
22
22
75
75
56
56
57
57
Wife 64
64
50
50
62
62
42
42
27
27
68
68
49
49
48
48