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

Multiple Choice

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