Use the given degree of confidence and sample 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.

Question: The mean replacement time for a random sample of 20 washing machines is 10.9 years and the standard deviation is 2.7 years. Construct a 90% confidence interval for the standard deviation, of the replacement times of all washing machines of this type. Interpret the result.