A clinical trial was conducted to test the effectiveness of a drug used for treating insomnia in older subjects. After treatment with the drug, 28 subjects had a mean wake time of 96.2 min and a standard deviation of 40.6 min. Assume that the 28 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 is effective? . . . Find the confidence interval estimate. min