Question: The management of a chain of package delivery stores wanted to predict weekly sales (in thousands of dollars) for individual stores based on the number of customers who made purchases. A random sample of 20 stores was selected, with the following results:

a. Set up a 95% confidence interval estimate of the average weekly sales for all stores that have 600 customers.

b. Set up a 95% prediction interval estimate of the weekly sales of an individual store that has 600 customers.

c. Explain the difference in the results obtained in (a) and (b).

d. Repeat (b) for 730 customers.

e. Explain the difference in the results obtained in (b) and (d).