A clinical trial was conducted to test the effectiveness of a drug used for treating insomnia in older subjects. After treatment with the drug, $20$ subjects had a mean wake time of $92\mathrm{.}2$min and a standard deviation of $42\mathrm{.}7$min. Assume that the $20$ sample values appear to be from a normally distributed population and construct a $90\%$ 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

$($Round to two decimal places as needed.$)$