The manager of the service department of a local car dealership has noted that the service times of a sample of 30 new automobiles has a standard deviation of 6 minutes. A 95% confidence interval estimate for the standard deviation of the service times for all their new automobiles is
A)16.047 to 45.722
B)4.778 to 8.066
C)2.93 to 6.31
D)22.833 to 65.059

Question

Quizplus · Accepted Answer

The confidence interval for the standard deviation is calculated using the chi-square distribution. Given a sample standard deviation of 6 minutes and a sample size of 30, the 95% confidence interval for the population standard deviation is approximately 4.778 to 8.066.

The Manager of the Service Department of a Local Car