Which of the following best describes a control chart?

A control chart is a statistical tool specifically designed for tracking process variability over time. It provides a visual representation of a process's performance by plotting data points in sequence and including control limits that indicate the expected range of variability in the process. This enables quality professionals to identify trends, shifts, or any unusual patterns indicating potential issues in the process, allowing for timely interventions.

Control charts are fundamental in quality control and management as they help ensure that a process remains stable and operates within defined limits. By monitoring data points against these control limits, organizations can maintain control over their processes, promoting consistency and improving quality. The ability to visualize data trends over time helps teams analyze performance and make data-driven decisions to foster continuous improvement.

In contrast, the other options do not accurately describe the primary function of a control chart. A list of errors observed during production focuses on specific mistakes rather than the variability of a process. A summary of customer complaints addresses feedback rather than process control and monitoring. A guide for employee training sessions concerns development and education, rather than tracking and analyzing process performance.