Bob
Your colleague has introduced a new idea into the Shewhart/Deming cycle
that I'm not sure Deming intended..
>A colleague of mine (Bob Dick) not only has a variation on this (Plan,
>Act, Reflect, Conclude),
My readings of Deming clearly indicate that it is a cycle, and a
continuous cycle at that. The last phase, Act has the following comments
by Deming (Out of the Crisis, pp88/89)
He annotates the 4th phase with the words "Study the results. What did we
learn? What can we predict?"
He then says "Step 4 of the Shewhart cycle (Study the results. What did
we learn from the change?) will lead (a) to improvement of any stage,
and (b) to better satisfaction of the customer for that stage. The
results may of course indicate no change at all, at least for now.
If the results are favourable, we may decide to go through the cycle
again, preferably under different environmental conditions, to learn
whether the favourable results of the first cycle were spurious or are
valid over a range of environmental conditions"
This clearly suggests that there isn't a conclusion: the journies around
the cycle are continuous as we squeeze as much of the non-special cause
variation out of a process.
Designing different experiments isn't always easy. I guess we prefer to
use the same test when we begin to observe errors occurring.
-- Roy Greenhalgh
--Roy Greenhalgh <rgreenh@attglobal.net>
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