Question

A clinical trial was conducted to test the effectiveness of a drug used for treating insomnia in older subjects. After treatment with the​ drug, 27 subjects had a mean wake time of 96.7 min and a standard deviation of 41.8 min. Assume that the 27 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 < sigma < _ min

My main issues are finding the right-tailed and left-tailed critical values.

Answer 1