Re: SIX SIGMA

["Alla Linetsky" <alinetsky@home.com>]

The 1.5 sigma 'long-term shift' in process mean is simply process
drift, a well-known condition. Machines get dirty, parts wear out,
cutters become dull, etc. The drift is generally not random, and there
are two approaches for dealing with it. The older approach was
developed by George Box in his book Evolutionary Operation of
Processes, published, I believe, in 1967 and long out of print.
However, most Engineering libraries in universities have it. The newer
approach is called Optimal Process Control which accounts for both
non-random and random variation in a process. The current guru on the
subject is Douglas C. Montgomery, and if you do a search on his name,
you will find a multitude of books and papers on this subject.

Otherwise, you're right; 6 Sigma is nothing more than a gimmicky
package for some ordinary process improvement tools, most of them
found in a $100 textbook.

Cheers,
Alla
=======================================================================