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, 15 subjects had a mean wake time of 90.6 min and a standard deviation of 43.4 min. Assume that the 15 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? Please help.

Answer 1

Given that the mean is

The 90% confidence interval for the standard deviation of wake time is given by

  

  

Therfore the 90% confidence interval for the sd is

Therfore the 90% confidence interval for the sd is (33.3671,63.3507).