The manager of a fleet of automobiles is testing two brands of radial tires and assigns one tire of each brand at random to the two rear wheels of eight cars and runs the cars until the tires wear out. the data (in kilometers) follow. find a 99% confidence interval on the difference in the mean life. car brand 1 brand 2 1 37132 34715 2 43879 41479 3 36240 35500 4 32100 31950 5 37210 38015 6 48360 47800 7 38200 37810 8 33500 33215