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 P09_16.xlsx.
a. Using the given sample data, find 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 would you advise the buyer to purchase? Would you even need a confidence interval to make this recommendation? Explain.
b. Repeat part a with a 99% confidence interval.
c. How are your results in parts a and b related to hypothesis testing? Be specific.