3. A sample of 220 items turned out during a given week by a certain process has an average weight of 2.57 lb and standard deviation of 0.57 lb. During the next week, a different lot of raw material was used, and the average weight of 220 items produced that week was 2.66 lb, and the standard deviation 0.48 lb. Assume normality.

(a) Construct a 95% confidence interval for the ratio of the population variances.

(Hint: You need to interpolate in the Fm,m,0.05 table or use one of the software packages.)

(b) On the basis of the interval calculated in (a), determine a 95% confidence interval for the differences of the population mean weights.