Managing for Quality and Performance Excellence 10th Edition by James Evans ,William Lindsay

Exercise 25

Note: Data for many of the problems in this chapter can be found in the Excel workbook C08Data.xlsx on the Student Companion Site. Click on the appropriate worksheet tab as noted in the problem (e.g., Prob. 8-6, etc.) to access the data.
Suppose that a refrigeration process at Coldfoods, Ltd. Has a normally distributed output with a mean of 27.0 and a variance of 1.21.
a. If the specifications are 27.0 ± 3.25, compute C p , C pk , and C pm. Is the process capable and centered?
b. Suppose the mean shifts to 26.0 but the variance remains unchanged. Recompute and interpret these process capability indexes.
c. If the variance can be reduced to 40 percent of its original value, how do the process capability indices change (using the original mean of 27.0)?