In Reply to Parent Post by artichoke
I'm curious as to why you have a logo "Stop X-bar/R Madness" ?
Machining, where constant tool wear effects results (Machine shops, SIC 3599, one of over 400 industry codes) is obviously a special case outside the general discussion.
I always find it amusing that precision machining is considered such an insignificant "special case".
Even if so, so what?
It exists, and its practitioners need
to understand that they have been sold a bill of goods with traditional charting systems. The madness is specifically for those that have been driven to use that chart when it does not apply - specifically precision machining. It has
driven people in precision machining mad - with ridiculously compressed control limits and over and under reported capabilities. Most have no idea what to do or where to go, and it has been my goal to correct that problem.
I do not doubt that there are truly naturally occurring normal processes, that meet the requirement of being set to a nominal value (mean), and stay at that value (some values a little lower, some values a little higher) without any interaction by an operator.
There may be a bunch of them in the other SIC codes - good for them. They can use the myriad of textbooks to get the information they need. They were written just for them
. I have even stronger belief that there are other exceptions - but that others affected by them have, too, been drilled into the normal fallacy, and the associated charting methods.
My point (and the point of my avatar) is to rid the madness in precision machining. I find it a very important cause, no matter how minute as a ratio of industry codes (as if they are equally distributed, and as if 200 or 300 more SIC codes might not have captured machining in their industry) or by any other "measure". This excuse of "being an exception" has been used by the SPC software suppliers, which do not provide the correct tool for precision machining to use - leaving them to fend for themselves with paper charts or Excel spreadsheets - or worst, the wrong control because they paid for garbage software sold by people who have no idea about how to control machining.
Others may have the opportunity to correct the rest of the world's statistical problems - at least for now.
Often when marketing a solution to a problem, you have to catch someone's attention to the fact that they have a problem. Apparently, your attention was caught - so there is clearly a level of success.
Besides, I was told I couldn't use my old avatar any longer.