Question

In order to test a new production method, 15 employees were selected randomly to try the

new method. The mean production rate for the sample was 80 parts per hour, and the standard

deviation was calculated to be 10 parts per hour.

CHAPTER 7. CONFIDENCE INTERVALS

120

a. Give a 95% confidence interval for the true mean production rate for the new method.

b. Interpret the interval in part a.

c. Suppose the confidence interval in part a is considered too wide. What sample size is

necessary to reduce the width of the confidence interval to one half of its original size?

d. What sample size is necessary to reduce the 95% margin of error to 1.5 parts per hour?

Answer 1