Baselining a Process

[James Robert Crow <jr1crow@mindspring.com>]

Steve Prevette is a person I have a lot of respect for when it come to
Statistics, but I want to question something he said is a recent post.
This is not an exact quote, but I belive he said that one reason for
removing "known" special causes from the calculation of control limits is
that if the "known" special causes were left in thic could affect a later
reading in which 7 points in a row below the average would show up as a
special cause.  I belive Steve is saying that by taking the "known" special
causes out, this would cause the mean to shift and the control limits to
close up, and this could mean that seven points in a row below average
would possibly no longer exist.  I wonder if that is true or if the seven
points in a row would still exist.  Perhaps someone, mabe Steve has
experienced this and could comment?



Robert Crow
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