Six Sigma For Dummies, 2nd Edition

Chapter 13

Assessing Capability: Comparing the Voices of the Customer and the Process

In This Chapter

Dealing with measures of yield and defect rate

Calculating and interpreting the sigma (Z) score of a process or characteristic

Using short- and long-term capability indices (CP, CPK, PP, and PPK)

This chapter is about two voices — the voice of the process and the voice of the customer — and the effect each has on the other. In Six Sigma, this relationship is called capability. Capability is how well the voice of your process or characteristic matches up with the voice of your customer, or in other words, how well your process performs in meeting customer expectations.

Following the DMAIC strategy, calculate capability in order to quantify, analyze, and communicate the performance of characteristics and processes relative to their requirements. With these capability metrics, you will know where to focus your attention and how to verify that you’ve made real improvement.

Working with Yield and Defect Rates

Creating a specification is one thing. Meeting that specification through your processes and characteristics is another. A central task of Six Sigma is to understand how well your ...