Refer to Problem 3.30.

(a) If we wish to detect a maximum difference in battery life of 10 hours with a probability of at least 0.90, what sample size should be used? Discuss how you would obtain a preliminary estimate of ????

2 for answering this question.

(b) If the maximum difference between brands is 8 hours, what sample size should be used if we wish to detect this with a probability of at least 0.90?