Question 6.15

6.15 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 ±10 minutes (0.17 hour) of the true mean .

  1. Based on your answer to part (b) in Exercise 6.14, should the sample size be larger or smaller than 150? Explain.
  2. What standard deviation of do you need such that 95% of all samples will have a mean within 10 minutes of ?
  3. Using the standard deviation you calculated in part (b), determine the number of students you need to sample.

6.15

(a) Larger, to decrease the standard deviation. (b) 0.085. (c) .