73. For the data of Exercise 69 we want a 95% condence interval for the ratio of population standard deviations.

a. Use the method of Section 10.5. Recall that this method requires the data to be normal, and the method is sensitive to departures from normality.

Check the data for normality to see if the F distribution can be used for the ratio of sample variances.

b. With a bootstrap sample of size 1000 use the percentile method to obtain a 95% con dence interval for the ratio of standard deviations.

c. Compare the two results and discuss the relationship of the results to those of Exercise 72.