You began a process charting procedure 5 weeks ago. Today, for the first time sample ranges are falling below the lower control limit on the range chart. You plan to stop the process, reasoning that customers will be upset. Your friend Dave argues, however, that the quality changes are due to an operator training program and are good.
What should you do?
A. It sounds like Dave is right, so try to evaluate the cause and continue producing this way.
B. It sounds like Dave is right so do nothing
C. Stop production and get the process right
D. Investigate the chart construction because values cannot fall below the lower control limit on a range chart