Quality control charts usually have a central line and upper and lower control limit lines. Which of the following is not a reason that the process being monitored with the chart should be investigated?
A) A large number of plots are close to the upper or lower control lines.
B) The behavior of the plots is erratic.
C) A single point falls above or below the control limits.
D) There is a change in raw materials or operators.
E) There is a run of five above the central line.

Question

Quizplus · Accepted Answer

The need for investigation in the context of quality control charts is typically triggered by statistical signals indicating potential out-of-control conditions, such as points outside the control limits or unusual patterns within the control limits. A change in raw materials or operators, while important to note, does not inherently signal a process issue on the chart itself without corresponding statistical evidence.

Quality Control Charts Usually Have a Central Line and Upper