Reducing Variation*

[David Kerridge <dfkerridge@mac.com>]

As promised in an earlier message, here are my thoughts
on why WED said that he had not told us to reduce variation.

It is true that if you apply the Deming Philosophy to a complete
organisation, variation does decrease. But so do a lot of other
things, such as costs, and conflict.

**       None of us would summarise Deming's message as
**      "Cut costs", even though it certainly does cut costs.

It may be that one reason why we associate the Deming
Management Philosophy with reducing variation is that
reduced variation is the first visible sign that it is working.
Reduced costs tend to appear later. And other benefits, such
as greater creativity, take even longer, as a rule - but they
may be the most important of all.

As Ned Hamson and other contributors have already said,
some kinds of variation (which we may prefer to call
variety) are necessary, or desirable.

Even when variation is bad,  not all *ways* of reducing
variation are good. If we jump in and use the obvious methods,
we may do more harm than good. The results may well
look good in the short term, but that makes the crude
methods even more dangerous.

For a start, we are liable to concentrate on reducing the
variation that we can easily measure, and ignore the
more important "invisible" variation. Or the way we
reduce variation in one part of the system may make
things worse in another part, or in the longer term.

If we apply the Deming Philosophy as he intended, we
may use variation as a warning that something is wrong.
If it is a special cause, we can remove the source without
doing harm. There may be counter-examples, but I haven't
met them yet. With common cause variation, we should try
to understand what is wrong with the system, that causes
such variation. Or perhaps, more often, what is  blocking
the natural tendency to improvement. This might be, for
example, a conflict of interest between departments.

The key is to improve the health of the system, not to treat
the obvious symptoms alone. So the message is very similar to
the remark that WED made about "Just in Time" management.

"If you apply my philosophy, you will achieve JIT
*if* it is appropriate, *when* it is appropriate, and
not otherwise."


Some of these ideas are set out in greater detail in the
article "Dr Deming's Cure for a sick System", which is
on the DEN files at

http://deming.ces.clemson.edu/pub/den/deming_kerridge.htm

Some rough notes on good and bad methods of reducing
variation are to be found at

http://homepage.mac.com/dfkerridge

Look for the section NYU, in which I have put notes used
at Dr Deming's research meetings at NYU. The most
relevant entry is NYU92b.
--
Best wishes

David

dfkerridge@mac.com