A point that plots below the lower control limit on the range chart:
I.should be ignored because lower variation is desirable.
II.may be an indication that process variation has decreased.
III.should be investigated for assignable cause.
A) I and II
B) I and III
C) II and III
D) II only
E) I, II, and III

Question

Quizplus · Accepted Answer

A point below the lower control limit on a range chart may indicate decreased process variation (II) and should be investigated for an assignable cause (III) to ensure it is not due to an error or special cause.

A Point That Plots Below the Lower Control Limit on the Range