A large buyer of household batteries wants to decide which of two equally priced brands to purchase. To do this, he takes a random sample of 100 batteries of each brand. The lifetimes, measured in hours, of the randomly chosen batteries are recorded in the file P10_16.XLS.

a. Using the given sample data, generate a 95% confidence interval for the difference between the mean lifetimes of brand 1 and brand 2 batteries. Based on this confidence interval, which brand should the buyer purchase?

b. Using the given sample data, generate a 99% confidence interval for the difference in the mean lifetimes of brand | and brand 2 batteries. Based on this confidence interval, which brand should the buyer purchase? ce How can your analyses in parts a and b be related to hypothesis testing?