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, 776, 760, 745, 759, 795, 756, 742, 740, 761, 749, 739, 747, 742 A process change is made which involves switching the type of catalyst used in the process. Following the process change, eight batch viscosity measurements are taken:

735, 775, 729, 755, 783, 760, 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.

(a) Formulate and test an appropriate hypothesis using  

0.10. What are your conclusions? Find the P-value.

(b) Find a 90% confidence interval on the difference in mean batch viscosity resulting from the process change.

(c) Compare the results of parts

(a) and

(b) and discuss your findings.