Certified Quality Engineer (CQE) Practice Exam 2025 - Comprehensive All-in-One Study Guide for Exam Success!

Cpk, or Process Capability Index, is a statistical measure used to assess a process's ability to produce output within specified limits. It quantifies how well a process can meet its specifications, factoring in both the process variability and the distance between the process mean and the target value of the specification limits. A higher Cpk value indicates a more capable process, meaning that the process is more consistent and is producing fewer defects.

This index is crucial for quality engineers because it helps in evaluating whether a process is adequately stable and capable of producing products that meet quality standards. A Cpk value above 1.33 is often considered acceptable in many industries, indicating that the process is capable of producing output with a high level of precision.

In contrast, R-charts and T1-charts are control charts used for monitoring process behavior over time but do not directly measure capability. The sigma level can indicate the level of defects or the relationship between mean and standard deviation but is less specific than Cpk in addressing the capability of a process with respect to specified limits. Thus, Cpk is the preferred index for measuring process capability in quality engineering.