A process may be in a state of control even if one sample mean is more than two standard deviations above the centerline.

Question

Quizplus · Accepted Answer

A process is considered out of control if any of the following occur:
- A single data point falls outside of the control limits (usually set at 3 standard deviations from the centerline)
- There are non-random patterns or trends in the data
- The sample mean shifts significantly from the centerline (usually 1-2 standard deviations or more)

However, if the sample mean is more than two standard deviations above the centerline but the data is otherwise random and there are no other patterns or trends, the process may still be considered in control. This is because random variation can still result in occasional extreme values, and it is only when these extreme values occur repeatedly or systematically that the process is considered out of control.

A Process May Be in a State of Control Even