A drug store chain has stores in four cities: 38 stores in Indianapolis, 45 in Louisville, 80 in St. Louis, and 70 in Memphis. Pharmacy sales in the four cities vary considerably because of the competition. The following sales data (in thousands of dollars) are available from a sample survey. Each of the cities was considered a separate stratum, and a stratified simple random sample was taken.

a. Estimate the mean pharmacy sales for each city (stratum).
b. Develop an approximate 95% confidence interval for the mean pharmacy sales in each city.
c. Estimate the proportion of stores with sales of $50,000 or more.
d. Develop an approximate 95% confidence interval for the proportion of stores with sales of $50,000 or more.

Indianapolis 50.3 41.2 15.7 22.5 26.7 20.8 Louisville St. Louis Memphis 48.7 59.8 28.9 36.5 89.8 96.0 77.2 81.3 16.7 38.4 51.6 42.7 45.0 59.7 80.0 27.6 88.3 94.2 76.8 35.1 48.2 57.9 18.8 22.0 74.3