A company claims that if its product is added to an automobile’s gasoline tank, the mileage per gallon will improve. To test the claim, 15 different automobiles are chosen and the mileage per gallon...

A company claims that if its product is added to an automobile’s gasoline tank, the mileage per gallon will improve. To test the claim, 15 different automobiles are chosen and the mileage per gallon with and without the additive is measured; the results are shown in Table 17.30. Assuming that the driving conditions are the same, determine whether there is a difference due to the additive at significance levels of (a) 0.05 and

(b) 0.01.