Plots of Sample Ranges Indicate That the Most Recent Value

Multiple Choice

Plots of sample ranges indicate that the most recent value is below the lower control limit. What course of action would you recommend?

A) Since there is no obvious pattern in the measurements, variability is in control.
B) One value outside the control limits is insufficient to warrant any action.
C) Lower than expected dispersion is a desirable condition; there is no reason to investigate.
D) The process is out of control; reject the last units produced.
E) Variation is not in control; investigate what created this condition.