Determining sample size. Recall the previous exercise. Suppose you want to use a sample size such that about 95% of the averages fall within ±0.05 hours (±3 minutes) of the true mean μ = 7.02.
(a) Based on your answer to part (b) in Exercise 7.18, should the sample size be larger or smaller than 400? Explain.
(b) What standard deviation of the sample mean do you need such that 95% of all samples will have a mean within 0.05 hours of μ?
(c) Using the standard deviation calculated in part (b), determine the number of students you need to sample.