a. Differences in age between husbands and wifes ( husband age minus wife age) of married couples have a distribution that approximately follows the normal curve with a mean of 1.5 years and a std of 2.1 years. negative differences indicate that the wife is older. approximately what percentage of marriages are wife older?
b. Give a value such that 40% of marriages have a larger age difference than this value. in other words, what is the 60th percentile of age difference.