Determining sample size. Refer to the previous exercise. Now you want to use a sample size such that about 95% of the averages fall within 6 10 minutes

(0.17 hour) of the true mean m 5 6.78.

(a) Based on your answer to part

(b) in Exercise 6.14, should the sample size be larger or smaller than 150? Explain.

(b) What standard deviation of x do you need such that 95% of all samples will have a mean within 10 minutes of m?

(c) Using the standard deviation you calculated in part (b), determine the number of students you need to sample.