Estimating a Population Variance: Example 02

EXAMPLE Confidence Interval for Penny Weights
Pennies are currently being minted with a standard deviation of 0.0165 g. New equipment is being tested in an attempt to improve quality by reducing variation. A simple random sample of 10 pennies is obtained from pennies manufactured with the new equipment. A normal quantile plot and histogram show that the weights are from a normally distributed population, and the sample has a standard deviation of 0.0125 g. Use the sample results to construct a 95% confidence interval estimate of 𝜎, the standard deviation of the weights of pennies made with the new equipment. Based on the results, does the new equipment appear to be effective in reducing the variation of the weights?