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 36,925 34,318
2 45,300 42,280
3 6,229 35,489
4 32,100 31,950
5 37,210 38,015
6 48,360 47,800
7 38,200 37,810
8 33,500 33,215
Does the confidence interval constructed in the previous step indicate that one brand is better than the other?