An independent consumer group tested radial tires from 2 major brands to find out whether there were any differences in the expected tread life. The data (in thousands of miles) are given here:
Brand 1 Brand 2
50 54 52 47 61 57 61 47 52 53
56 51 51 48 56 57 56 53 67 58
53 43 58 52 48 62 56 56 62 57
a. Analyze these data using appropriate parallel boxplots.
b. Conduct the appropriate hypothesis test using a 0.05 significance level.
c. Determine the 95% confidence interval on the true mean difference in the tread lives.
d. What did you assume to do these analyses? Can you evaluate how well these data meet the assumptions? If yes, determine how comfortable you are with them. If not, explain why.