Jay Warner writes:
>The 'party line' is to take the first 30 or so points, calculate
>limits, throw out any outside ones & add more at the end, until you
>have 30 points, all of which are inside the control limits.
Actually, I have heard the opposite. Out-of-control points do not have THAT much of an impact on the control limits, so that recomputing control limits after removing out of control points is not a good use of your time. Wheeler makes the suggestion that the time spent fine tuning the chart might be better spent investigating why the original points are out of control.
I am not an SPC guru, though, so take my advice with a grain of salt.
Steve Simon, [EMAIL PROTECTED], Standard Disclaimer.
The STATS web page has moved to
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