Which of the following statements is correct regarding control charts?
I. Specification limits are the same as control limits
II. If there is no assignable cause of variation the process is in control
III. A shift in the or average will show up on the X portion of the X and R chart
A) I and II are true
B) I and III are true
C) II and III are true
D) all the above are true
E) none of the above is true

Question

Quizplus · Accepted Answer

Statement I is incorrect because specification limits are different from control limits. Specification limits are the maximum and minimum values allowed by the customer or regulatory standards, while control limits are determined by the process variability. Statement II is true as a process is considered in control when all the variations are within the control limits and there are no assignable causes of variation present. Statement III is true as a shift in the process average will be reflected in the X-chart of the X and R chart. Therefore, choice C is the correct one.

Which of the Following Statements Is Correct Regarding Control Charts