Six Sigma Green Belt Certification Practice Exam 2026 - Free Six Sigma Practice Questions and Study Guide

The correct choice is that Cpk is indeed a process performance index. The focus of the question is on identifying what is not classified as such among the provided options.

Pp, Ppk, and Cpm are all statistical measures that provide insights into how well a process is performing or meeting specifications under varying conditions. Pp (Process Potential) assesses how capable a process could be if it were centered on the target specification, representing the overall spread of the process. Ppk (Process Performance Index) adjusts for the effect of centering, providing a clearer picture of how consistently a process meets specifications. Cpm (Scaled Process Performance Index) additionally considers the target value, which also emphasizes the importance of being centered on target for an optimal process performance.

Therefore, all the other options are recognized as process performance indices, each serving a distinct role in evaluating process capability.