This data set contains the ages of the husband and the wife for 20 couples. We want to know what the difference is between the ages of husbands and wives

This data set contains the ages of the husband and the wife for 20 couples. We want to know what the difference is between the ages of husbands and wives. Since this data is paired (and clearly not independent) we should not use the 2-Sample T Interval or 2-Sample T Test.
Instead consider the pairwise differences.
Using our calculator, enter the Age of Husband in L1, the Age of Wife in L2. Move your cursor over L3 and type L1-L2… enter. L3 will fill with the pairwise differences.  We will treat this as our data set.
a) Create a 90% confidence interval for the true
(pairwise) differences and interpret it in the context
of the problem