Is housework hazardous to your health? A study in Public Health Reports compared the life expectancies of 25-year-old white women in the labor force to those who are housewives. How large a sample would have to be taken from each group in order to be 95% confident that the estimate of difference in average life expectancies for the two groups is within 1 year of the true difference in average life expectancies? Assume that equal sample sizes will be selected from the two groups and that the standard deviation for both groups is approximately 15 years.