Question

CRA CDs Inc. wants the mean lengths of the “cuts” on a CD to be 140 seconds (2 minutes and 20 seconds). This will allow the disk jockeys to have plenty of time for commercials within each 10-minute segment. Assume the distribution of the length of the cuts follows a normal distribution with a standard deviation of eleven seconds. Suppose that we select a sample of 12 cuts from various CDs sold by CRA CDs Inc. Use Appendix B.1 for the z-values.

a. What can we say about the shape of the distribution of the sample mean?

Sample mean             (Click to select)  Normal  Uniform  Binomial

b. What is the standard error of the mean? (Round the final answer to 2 decimal places.)

Standard error of the mean             seconds.

c. What percentage of the sample means will be greater than 147 seconds? (Round the final answer to 2 decimal places.)

Sample means             %

d. What percentage of the sample means will be greater than 132 seconds? (Round the final answer to 2 decimal places.)

Sample means             %

e. What percentage of the sample means will be greater than 132 but less than 147 seconds? (Round the final answer to 2 decimal places.)

Sample means             %

Answer 1