1.A polymer is manufactured in a batch chemical process. Viscosity measurements are normally made on each batch, and long experience with the process has indicated that the variability in the process is fairly stable with = 20. Fifteen batch viscosity measurements are given as follows:

724, 718, 778, 760, 745, 759, 795, 756, 742, 740, 761, 749, 739, 747, 740

A process change that involves switching the type of catalyst used in the process is made. Following

the process change, eight batch viscosity measurements are taken:

735, 770, 729, 755, 783, 765, 738, 780

Assume that process variability is unaffected by the catalyst change. If the difference in mean batch

viscosity is 10 or less, the manufacturer would like to detect it with a high probability. Find a 90%

confidence interval on the difference in mean batch viscosity resulting from the process change and

give a practical interpretation.