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, 22 subjects had a mean wake time of

97.7 min and a standard deviation of 40.4 min. Assume that the 22 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 less than< sigma σ less than <nothing min

Answer 1

We are given . The 95% confidence interval for the variance is given by the formula

Substituting the values, we get

The confidence interval for the standard deviation is