A clinical trial was conducted to test the effectiveness of a drug used for treating insomnia in older subjects. After treatment with thedrug, 20 subjects had a mean wake time of 95.2 min and a standard deviation of 40.7 min. Assume that the 20 sample values appear to be from a normally distributed population and construct a 95% confidence interval estimate of the standard deviation of the wake times for a population with the drug treatments. Does the result indicate whether the treatment iseffective?

Find the confidence interval estimate.

(Round to two decimal places asneeded.)