# sum of the sample standard deviations for 25 subgroups of size 4

## Question: A new process is started, and the sum of the sample…

A new process is started, and the sum of the sample standard deviations for 25 subgroups of size 4 is 750. If the specifications are 70080:

- a) What is the process capability index?
- b) What action would you recommend?
- c) What is the Cpkvalue for this process when the process average is 700, 780, and 820? Explain and say in which case the process is centered.
- d) Compute the rejection rates in each case of question c)
- e) A four sigma program is introduces at the company. The lower specification limit (LSL) and the process σ remain the same. Describe the Cp and Cpk reject rates and show the X-bar and R chart limits, using the same sample size.
- f) Repeat for a six sigma program with 1.5σ shift, with the process average and sigma remaining the same.