The thicknesses of n = 41 glass sheets made using process A are measured and the statistics  = 3.04 mm and sx = 0.124 mm are obtained. In addition, the thicknesses of m = 41 glass sheets made using process B are measured and the statistics  = 3.12 mm and sy = 0.137 mm are obtained. Use a pooled variance procedure to answer the following questions.
(a) Does a two-sided hypothesis test with size α = 0.01 accept or reject the null hypothesis that the two processes produce glass sheets with equal thicknesses on average?
(b) What is a two-sided 99% confidence interval for the difference in the average thicknesses of sheets produced by the two processes?
(c) Is there enough evidence to conclude that the average thicknesses of sheets produced by the two processes are different?
(This problem is continued in Problems 9.3.15 and 9.6.11.)