Acme Delivery offers three different shipping rates for packages fewer than 5 pounds delivered from Maine to the West Coast: regular, $3; fast, $5; and lightning, $10. To test the quality of these services, a major mailorder retailer shipped 15 packages at randomly selected times from Maine to Tacoma, Washington. The packages were shipped in groups of three by the three services at the same time to reduce variation resulting from the shipping day. The following data show the shipping cost, X, and the number of days, Y, in (x, y) pairs:
13, 72 15, 52 110, 22 13, 92 15, 62 110, 52 13, 62 15, 62 110, 12 13, 102 15, 72 110, 42 13, 52 15, 62 110, 42
a. Describe the data numerically (covariance and correlation).
b. Discuss the value of the higher-priced services in terms of quicker delivery.