From: alfredb@pogo.wv.tek.com (Alfred Brown)
Newsgroups: comp.software-eng
Subject: Re: Wanted: Info on "six-sigma" system
Keywords: sigma, Motorola
Date: 16 Oct 92 16:14:57 GMT
Article-I.D.: pogo.13773
Reply-To: alfredb@pogo.WV.TEK.COM
Distribution: usa
Organization: Tektronix, Inc. Wilsonville

> In article <1992Oct9.210152.9844@awdprime.austin.ibm.com>, alan@auntbea.austin.ibm.com (Alan R. Weiss) writes:
> |>In article <1992Oct9.085040.2992@cbfsb.cb.att.com> djones@cbnewsg.cb.att.com (david.jones) writes:
> |>>
> |>>Has anybody heard of "six-sigma" ?

> |>This is the Quality Program of Motorola.  It may be proprietary
> |>information of Motorola Corporation (HQ:  Schaumberg, Illinois USA).
> 

The publication "Electronic Business" mentions six-sigma whenever there is an
article about Motorola.  Here is a small inset from the Oct. 16,'89 issue 
(pg.66):
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'MOTOROLA SEEKS ELUSIVE "SIX SIGMA" TARGET'

"To get dramatic results, Motorola Inc. executives agreed that they needed to
strive for very tough goals.  But when they fixed on a goal they dubbed "Six
Sigma" as their 1992 target for improving operations and products, even the 
most avid proponents of quality were impressed.

"What does Six Sigma mean?  In short, it means that Motorola wants to be free
of errors and defects 99.9997% of the time in all that it does.  That means no
more than 3.4 defects per million units.

"The name of the effort comes from statistics.  Sigma is a statistical measure
of variability around the average.  In a normal distribution, represented by 
the familiar bell-shaped Gaussian curve, the values falling within one standard
deviation, or one sigma, of the mean, or average value, include 68.3% of the 
total.  Move out to three standard deviations, or three sigma, to either side
and about 99.7% are included.  But that would still be 2,700 defects per 
million.

"It can be shown that a robust design, one that can accept twice the normal 
variation of the process, can be expected to have no more than 3.4 parts per
million defective for each characteristic, instead of 2,700 (even if the normal
distribution curve were to shift by as much as 1.5 sigma off center).  Thus,
Six Sigma covers 99.9997% of the distribution under the curve.

"Take the example of circuit boards coming off a production line.  Shooting
for Six Sigma means Motorola wants 99.9997% of the boards to perform within
specifications.  Consider a 10,000-ohm resistor that goes onto the board.  One
way to keep the board's performance within the Six Sigma range would be to 
design it so that an individual board would still work within specs even if
the resistor happened to be very far from the mean.  By allowing more variation
around the average value of 10,000 ohms, say plus or minus 5,000 ohms, the goal
of 99.9997% of the boards free of defects might be achieved.

"Another approach, of course, is to keep the process variation within very
narrow values through tight control.  In other words, the variation of the
resistors themselves would be kept within a very tight range.
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The first I heard about Six-Sigma was when Motorola won the Malcolm Baldrige 
National Quality Award in 1988.  According to the rules, the winners must agree
to share information on their approach to quality with other American firms.
Motorola sponsors seminars and describes it methods to suppliers and 
competitors.  
What Motorola is specifically doing in its software organizations I do not
know, but it would seem obvious that something is being done to achieve an
overall six-sigma quality level.
-- 
Alfred Brown, Sr. Software Engineer, Graphics Printing & Imaging Division,
Tektronix, Inc.  P.O. Box 1000  MS 63-424  Wilsonville, Oregon  97070-1000
Ph:(503) 685-3698      FAX:(503) 682-1183  email: alfredb@pogo.wv.tek.com
disclaimer: I do not speak for Tektronix, Inc.,  nor does it speak for me.