A tire manufacturer is interested in testing the fuel economy for two different tread patterns. Tires of each tread type were driven for 1000 miles on each of 9 different cars. The mileages, in miles per gallon, were as follows: Car Tread A Tread B 1 24.6 20.0 2 22.3 19.0 3 24.0 22.7 4 27.1 22.9 5 22.2 20.5 6 23.3 23.4 7 22.9 21.7 8 19.6 17.8 9 27.5 26.0 Send data to Excel Part: 0 / 20 of 2 Parts Complete Part 1 of 2 (a) Construct a 99% confidence interval for the mean difference in fuel economy. Let d represent the mileage of tread pattern A minus the mileage of tread B. Use tables to find the critical value and round the answers to at least two decimal places. A 99% confident that the mean difference in fuel economy is