Refer to Exercise 5.74.
In exercise

a. The cars in the study appear to have grossly different mileages before the devices were installed. Use the change data to test whether there has been a significant gain in mileage after the devices were installed. Use a = .05.
b. Construct a 90% confidence interval for the mean change in mileage. On the basis of this interval, can one reject the hypothesis that the mean change is either zero or negative? (The two-sided 90% confidence interval corresponds to a one- tailed a = .05 test by using this decision rule: Reject H0: μ ‰¥ μ0 is greater than the upper limit of the confidence interval.)

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installation. The data are recorded here. Car 12 3 4 5 67 89 10 Before (pg 19.1 29.9 176 20.2 23.5 26.8 21.7 25.7 19.5 28.2 10 2322 4.25 After (mpg) 25.8 237 28.7 25.4 32.8 192 29.6 22.3 25.7 20.1 10 25.33 425 Change (mpg 6.7 -62 111 5.2 9.3-76 7.9-34 6.2 -8.1 10 2.11 754