I remember writing an article a few years ago about this same topic, though not nearly as sophisitcatedly as Dr. Wheeler. I ran into this problem many times in industry where someone in management felt the control limits were too wide. He just did not understand that the process determines the UCL and LCL, not the specifications or the desires of management. Long story short: These so-called "Action Limits" should be called "Tampering Limits"! "Tamper, tamper is the way. Off we go to the milky way."
I remember writing an article a few years ago about this same topic, though not nearly as sophisitcatedly as Dr. Wheeler. I ran into this problem many times in industry where someone in management felt the control limits were too wide. He just did not understand that the process determines the UCL and LCL, not the specifications or the desires of management. Long story short: These so-called "Action Limits" should be called "Tampering Limits"! "Tamper, tamper is the way. Off we go to the milky way."