Question

For a sample of 9 vehicles, the mileage (in 1000s of miles) at which the original front brake pads were worn to 10% of their original thickness was measured, as was that of the rear brakes. The results are as follows.

Rear 41.2 35.8 46.6 46.9 39.2 51.5 51.0 46.0 47.3

Front 32.5 26.5 35.6 36.2 29.8 40.9 40.7 34.5 36.5

(a) Construct at 99% confidence interval for the difference in mean lifetime between the front and rear brakes.

(b) An automotive engineer claims that the mean lifetime of rear brake pads is more than 10, 000 miles more than the mean lifetime of front brake pads. Does the confidence interval support this claim?

Answer 1