In a test of the effectiveness of a device that is supposed to increase gasoline mileage in automobiles, 12 cars were run over a prescribed course both with and without the device. The mileages are given below. Conduct hypothesis test at ?=.05.
Car Without Device With Device
1 21 20.6
2 30 29.9
3 29.8 30.7
4 27.3 26.5
5 27.7 26.7
6 33.1 32.8
7 18.8 21.7
8 26.2 28.2
9 28 28.9
10 18.9 19.9
11 29.3 32.4
12 21 22