Answer:
The correct answer is letter "A": Common cause investigation.
Explanation:
Statistical Process Control or SPC refers to the implementation of different statistical techniques aiming to regulate production processes. SPC uses charts to record data in an attempt to spot irregular events in manufacturing. Two types of process variation are identified: common cause variation (proper of the production) and special cause variation (external of the production).
Therefore, common and cause investigation is not a step in SPC. It is a type of process variation.
