is housework hazardous to your health? a study in public health report compares the life expectancies of 25-year-old white women in the labor force with those who are housewives. how large a sample would have to be taken from each group in order for you to be 95% con dent that the estimate of the difference in mean life expectancies for the two group is within 1 year of the true difference? assume that equal sample sizes will be selected from the two groups and that the standard deviation for both groups is approximately 15 years.