Six Sigma Black Belt Certified Practice Exam

A control chart is a vital tool in quality control that specifically focuses on monitoring the mean and variability of a process over time. It provides a visual representation of how a process behaves and allows practitioners to track changes in the process data.

By plotting data points over time, a control chart enables professionals to identify trends, shifts, and outliers that may indicate whether the process is in control or if it needs attention. The central line on the chart represents the average (mean) of the process data, while the control limits help define the acceptable range of variation. When data points fall outside these control limits, it can signal the presence of special causes of variation that require investigation.

Focusing on mean and variability is crucial because it helps ensure that processes remain stable and predictable, which is essential for maintaining quality and meeting customer expectations. The other options do not directly relate to the function of control charts: they deal with specific outcomes (like costs or customer satisfaction) rather than the underlying process behaviors that control charts are designed to monitor.