Chapter 5.12, Problem 39E

A consumer testing agency wants to evaluate the claim made by a manufacturer of discount tires. The manufacturer claims that its tires can be driven at least 35,000 miles before wearing out. To determine the average number of miles that can be obtained from the manufacturer’s tires, the agency randomly selects 60 tires from the manufacturer’s warehouse and places the tires on 15 cars driven by test drivers on a 2-mile oval track. The number of miles driven (in thousands of miles) until the tires are determined to be worn out is given in the following table.

1. a. Place a 99% confidence interval on the average number of miles driven, μ, prior to the tires wearing out.
2. b. Is there significant evidence (α = .01) that the manufacturer’s claim is false? What is the level of significance of your test? Interpret your findings.