The times required to check out customers in a supermarket and the corresponding values of purchases are shown in Table P-4. Answer parts a, b, e, and f of Problem 3 using these data. Give a point forecast and a 99% interval forecast for Y if X = 3.0.

In Problem 3
a. Does a significant relationship exist between advertising expenditures and sales?
b. State the prediction equation.
e. State the amount of unexplained variation.
f. State the amount of total variation.

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TABLE P-4 Time Required Value of Time Required Value of for Checkout Purchase for Checkout Purchase (minutes) 30.6 30.5 2.4 42.2 21.8 (minutes) 1.8 4.3 2.6 1.3 3.6 4.1 40.1 2.0 15.5 6.5 5.7