A consumer-protection magazine was interested in comparing tires purchased from two diff...

A consumer-protection magazine was interested in comparing tires purchased from two different companies that each claimed their tires would last 40,000 miles. A random sample of 10 tires of each brand was obtained and tested under simulated road conditions. The number of miles until the tread thickness reached a specified depth was recorded for all tires. The data are given next (in 1,000 miles).

a. Plot the data and compare the distributions of longevity for the two brands.

b. Construct 95% confidence intervals on the means and standard deviations for the number of miles until tread wearout occurred for both brands.

c. Does there appear to be a difference in wear characteristics for the two brands? Justify your statement with appropriate plots of the data, tests of hypotheses, and confidence intervals.