Use the Given Degree of Confidence and Sample Data to Find

Multiple Choice

Use the given degree of confidence and sample data to find a confidence interval for the population standard deviation ?.
Assume that the population has a normal distribution. Round the confidence interval limits to the same number of decimal places as the sample standard deviation.
-The mean replacement time for a random sample of 20 washing machines is 9.4 years and the standard deviation is 2.5 years. Construct a 99% confidence interval for the standard deviation, ?, of the replacement times of all washing machines of this type.

A) $1.8 \mathrm { yr } < \sigma < 4.2 \mathrm { yr }$
B) $1.8 \mathrm { yr } < \sigma < 3.9 \mathrm { yr }$
C) $1.7 \mathrm { yr } < \sigma < 4.8 \mathrm { yr }$
D) $1.8 \mathrm { yr } < \sigma < 5.3 \mathrm { yr }$