A researcher wanted to determine if using an octane booster would increase gasoline mileage.

A researcher wanted to determine if using an octane booster would increase gasoline mileage. A random sample of seven cars was selected; the cars were driven for two weeks without the booster and two weeks with the booster. Use the definitions of X1 and X2 as given in the table. Consequently, D = X1–X2.Gasoline MileageWithout booster, X1(mpg)Gasoline MileageWith booster, X2(mpg)21.223.825.425.620.922.427.628.322.824.527.328.823.425.2