Plastic sheets made by a machine are periodically monitored for fluctuations in thickness. If the true standard deviation in thickness exceeds 2.0 millimeters, there is cause for concern about product quality. Past experience indicates that thickness measurements of plastic sheets are normally distributed. Suppose that thickness measurements for a random sample of 24 sheets produced in a particular shift were taken, and the sample statistics were computed as follows: Sample size: n=24 sheets sample standard deviation s= 2.36 millimeters
Compute the 95% confidence interval estimate of the standard deviation of the thickness
Test the alternate hypothesis that the population standard deviation is larger than 2.0 millimeters