Which statement describes run charts vs control charts?

• A. Run charts plot data over time without control limits; control charts add statistical control limits to distinguish common vs special causes.
• B. Run charts require statistical control limits.
• C. Control charts are used only in manufacturing.
• D. Run charts are the same as control charts.

Answer: (A)

The key idea here is that run charts and control charts serve different purposes in monitoring a process over time. A run chart simply plots data points in sequence to reveal patterns, trends, shifts, or cycles, but it does not include any statistical boundaries. Because there are no control limits, you can see what happened, but you can’t formally tell whether the variation you observe is just random (common causes) or indicates something needing investigation (special causes).

Control charts build on that by adding a centerline and statistically derived control limits. These limits help distinguish ordinary, common-cause variation from signals that suggest a process is out of control due to a special cause. When data fall outside the limits or show nonrandom patterns, it prompts a closer look and potential corrective action. This approach is widely used beyond manufacturing, including in healthcare, for ongoing process monitoring and improvement.

So the statement is best because it accurately captures that run charts plot data over time without control limits, while control charts include limits to help identify when variation points to a special cause. The other statements are not correct: run charts do not require control limits, control charts aren’t limited to manufacturing, and run charts are not the same as control charts.