Certified Production & Operations Manager (POM) Practice Exam

What does it mean when a control chart is outside of control limits?

1. It is a sign of normal variation.

2. It suggests no further action is needed.

3. It indicates the process is likely out of control.

4. It proves that sampling was inaccurate.

The correct answer is: It indicates the process is likely out of control.

When a control chart shows data points that fall outside of the established control limits, it indicates that the process is likely out of control. Control limits, which are determined based on statistical analysis, define the expected variation in a stable process. When points exceed these limits, it signals that there may be special causes of variation present that have not been accounted for by the normal operating conditions of the process. This means that some unexpected issues or variations are affecting the process, warranting investigation and potential corrective action. The presence of control chart points outside of these limits prompts analysts and process owners to examine the underlying factors contributing to the deviations, facilitating the identification of problems that could affect quality or performance. Understanding this helps ensure that processes remain stable and produce outputs consistent with quality standards.