Question

A consumer products testing group is evaluating two competing brands of tires, Brand 1 and Brand 2. Though the two brands have been comparable in the past, some technological advances were recently made in the Brand 2 manufacturing process, and the consumer group is testing to see if Brand 2 will outperform Brand 1. Tread wear can vary considerably depending on the type of car, and the group is trying to eliminate this effect by installing the two brands on the same random sample of 10 cars. In particular, each car has one tire of each brand on its front wheels, with half of the cars chosen at random to have Brand 1 on the left front wheel, and the rest to have Brand 2 there. After all of the cars are driven over the standard test course for 20,000 miles, the amount of tread wear (in inches) is recorded, as shown in Table 1.

Car Brand 1 Brand 2 Difference (Brand 1 - Brand 2) 1 0.342 0.323 0.019 2 0.326 0.287 0.039 3 0.374 0.289 0.085 4 0.353 0.302 0.051 5 0.309 0.317 -0.008 6 0.202 0.185 0.017 7 0.238 0.197 0.041 8 0.289 0.292 -0.003 9 0.390 0.357 0.033 10 0.222 0.120 0.102

Table 1

Answer 1