A major automobile manufacturer wants to know whether there is any difference in the average mileage of four different brands of tires (A, B, C, and D), because the manufacturer is trying to select the best supplier in terms of tire durability. The manufacturer selects comparable levels of tires from each company and tests some on comparable cars. The mileage results follow.

Use α = .05 to test whether there is a significant difference in the mean mileage of these four brands. Assume tire mileage is normallydistributed.

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