With reference to Exercise 11.25, use the large-sample confidence- interval formula of Exercise 11.19 to construct a 98% confidence interval for the standard deviation of the time it takes a mechanic to perform the given task.
In exercise
A food inspector, examining 12 jars of a certain brand of peanut butter, obtained the following percent-ages of impurities: 2.3, 1.9, 2.1, 2.8, 2.3, 3.6, 1.4, 1.8, 2.1, 3.2, 2.0, and 1.9. Based on the modification of Theorem 11.1 of Exercise 11.7, what can she assert with 95% confidence about the maximum error if she uses the mean of this sample as an estimate of the average percentage of impurities in this brand of peanut butter?