Detailed Explanation:
The correct answer is C. Control chart.
A control chart is the primary tool used to determine whether a process is operating with only common cause variation or whether special cause variation is present.
Control charts display process data over time against statistically determined control limits. They help identify:
Unusual patterns
Points outside control limits
Non-random variation
Signals that suggest the process is out of statistical control
When these signals appear, they indicate the possible presence of special causes that require investigation.
Why the other options are incorrect:
A. Fishbone diagram
A fishbone diagram is used to identify possible causes of a problem, not to determine statistically whether special cause variation exists.
B. Cause and effect diagram
This is another name for a fishbone diagram. It supports root cause exploration, not statistical detection of variation type.
D. Pareto chart
A Pareto chart helps identify the most significant categories of problems or defects, but it does not determine whether a process contains special cause variation.
Quality Management Excellence reference basis:
This answer is aligned with Quality Management Excellence principles that emphasize:
data-based process control,
distinguishing signal from noise,
and using the correct analytical method for process evaluation.
A control chart is the proper tool because it directly supports the interpretation of process stability and variation behavior, which is essential to effective quality management.