With reference to Exercise 25, use the large-sample confidence-interval formula of Exercise 19 to construct a 98% confidence interval for the standard deviation of the time it takes a mechanic to perform the given task.
Exercise 25
To estimate the average time required for certain repairs, an automobile manufacturer had 40 mechanics, a random sample, timed in the performance of this task. If it took them on the average 24.05 minutes with a standard deviation of 2.68 minutes, what can the manufacturer assert with 95% confidence about the maximum error if he uses 
= 24.05 minutes as an estimate of the actual mean time required to perform the given repairs?