A quality control chart is used to monitor the customer wait time at a local call center. Sample means of five times are averaged and plotted over time. The last fifty sample means are randomly distributed between the upper and lower control limits. The process is
A) out-of-control.
B) in-control.
C) improving.
D) showing assignable variation.

Question

Quizplus · Accepted Answer

The fact that the last fifty sample means are randomly distributed between the upper and lower control limits indicates that the process is stable and in control. If the points were not randomly distributed, it would indicate the presence of assignable causes of variability and the process would be out-of-control. However, since it is stable, it is not improving or showing assignable variation.

A Quality Control Chart Is Used to Monitor the Customer