The lower and upper control limits of an $\bar { x }$ control chart are usually set at:
A) $\pm$ one standard error from the centerline.
B)$\pm$ two standard errors from the centerline.
C) $\pm$ three standard errors from the centerline.
D) None of these choices.

Question

Quizplus · Accepted Answer

The most common convention for setting control chart limits is to use three standard errors from the centerline. This ensures that 99.7% of the data falls within the control limits, assuming the data is normally distributed.

The Lower and Upper Control Limits of An xˉ\bar { x }xˉ

The Lower and Upper Control Limits of An $\bar { x }$