The primary purpose of a control chart is to determine the stability of a process.

• A. To determine the stability of a process
• B. To maximize production speed
• C. To minimize inventory
• D. To train staff

Answer: (A)

Control charts are used to determine if a process is statistically stable and predictable. By plotting a key quality measure over time against calculated control limits, you can see whether the variation observed is just natural (common causes) and stays within expected bounds, which indicates a stable process. If the data show patterns, runs, or points outside the limits, that signals special causes of variation and instability, prompting investigation and potential improvement. This focus on stability and detectability of signals is what makes it the primary purpose. They aren’t intended to maximize production speed, minimize inventory directly, or train staff.