Six Sigma - The Beginnings and History


David McGan

How would the "Six Sigma" philosophy be best quantified? "Statistical technique", Continuous Improvement activity, Lean Manufacturing, or "all of the above?"


Fully vaccinated are you?
I don't know about lean manufactuiring, but 6 sigma fits Statistical Techniques and Continuous Improvement.


-> Date: Tue, 23 Sep 1997 17:44:22 -0400
-> From: Dan Rand
-> Subject: 6 Sigma history
-> Let me add another perspective to Six Sigma. IBM executives started
-> visiting Motorola headquarters shortly after they won their Baldrige, to
-> benchmark and pick up some of their quality practices. First on the list
-> was Six Sigma. I was an internal statistical methods consultant and
-> quality engineer at IBM in Rochester, MN at this time. We were forced to
-> adapt Six Sigma at our site, even though we had the same concerns that have
-> been listed in recent discussions in this forum. Six Sigma was present, but
-> not dominant, by the time our IBM site won a Baldrige in 1990.
-> Six Sigma was being implemented corporate-wide at the insistence of some
-> highly placed IBM executives. There were complaints and discussions
-> throughout IBM until the leading technologist in the company called 15-20
-> statisticians and quality managers together to publish a position paper on
-> Six Sigma. We were encouraged to believe that our opinions and factual
-> evidence were going to get a hearing.
-> We expressed concern with Motorola s misuse of statistical terms, the thin
-> theoretical and practical evidence for the 1.5 sigma shift, and the dubious
-> means of counting defects and opportunities for defects. Our position
-> paper was finally regarded as too disruptive to IBM s progress in defect
-> reduction, which management wanted to credit to Six Sigma policies. The
-> position paper was never distributed beyond the team that created it.
-> Six Sigma is rarely mentioned around IBM anymore. It quietly disappeared
-> with the radical downsizing that took place from 1991-93, even though it
-> was always touted as not just another quality program. I believe its
-> disappearance did occur primarily because many of its champions either left
-> IBM, or had too many higher priorities left to cover. I left IBM in the
-> downsizing, along with 80statisticians).
-> Most interestingly, when I have run across Motorola employees in the years
-> since, they consistently state that there is still a passionate pursuit of
-> defect reduction and quality improvement at Motorola, which more or less
-> still occurs under the banner of Six Sigma. We might dismiss the whole Six
-> Sigma approach as sloganism, but we must realize that large corporations
-> necessarily put a simple label on programs that they want to implement
-> corporate-wide. Seemingly, everyone in Motorola knows just what you are
-> talking about when you mention Six Sigma, even if it is different than what
-> we quality experts and statisticians know it is. Their quality improvement
-> process has stood the test of time.
-> IBM could not sustain its Six Sigma program, probably because of business
-> factors. Every organization and their circumstances are a little
-> different. I respect General Electric s CEO and their attempt to fully
-> embrace quality improvement. They may succeed if they get their entire
-> workforce to approach quality improvement with a simple, tools oriented,
-> common sense process underneath the slogan of Six Sigma.
-> Daniel R. Rand
-> Consultant, Rand Quality Technologies

David McGan

Thanks, Marc, for the information from IBM. Although I had heard a little about 6 Sigma and its successes in the past (mostly associated with Motorola), I'm trying to get much more intimately acquainted with it since my company's President asked me to. So far, I've seen much more of the "mixed emotions" as reported by IBM staffers than completely positive reports. I'm attending a 6-Sigma symposium next week and so should hear plenty of the "pros" of 6-sigma. However, I would also welcome additional input from the less biased "real world." That way, I can make the most informed recommendation as to the direction our company should proceed. We certainly don't want to foster a "flavor of the month" perception with our team members.


Fully vaccinated are you?
I know I went into this at length somewhere but I can't find where. I included the snippet as it pretty well states a view I feel has to be considered - one specific is the 'theroetical' 1.5 sigma shift which very, very often comes up. There are some real strong opinions on that shift.

I do have a copy of an internal Motorola booklet titled "Six Sigma Process Control" from 1993 but I can't post it or copy it because it's proprietary - internal to Motorola. It's almost 50 pages and is really informative. It's sorta a short version of a book I have from IBM's Quality Institute (approx. 200 pages). Both take a high level approace but IBM's is more extensive (even covers Design of Experiments!)

Anyway, hope the info helps. If you have an friends internal to Motorola you might try to pry a copy of their book. I got the IBM book some years ago (it's from November 1984) and can't remember where. It's a good one.

The point is - both books give parts of what QS9000 lingo calls APQP - which is just a good, sound business system - from product conception / contract review to end of product life. I can't stress highly enough the importance of a robust (for lack of a better word) design 'phase'. If you fail that phase control and things like 6 sigma won't mean much - you cripple yourself early.

Phew - I gotta get back to work!


Fully vaccinated are you?
Date: Sat, 1 May 1999 15:40:58 -0400
From: RNav
Subject: Re: FW: Six Sigma

In a message dated 4/27/99 11:36:44 AM, NML writes:

>Dear Mr Robert,
> we are a flow control equipment manufacturing
>engineering company with ISO 1901 accreditation. Two years ago we have
>started BPR in a big way and concentrated to improve key processes. How
>ever we have not improved the quality management process. Of late we
>have started getting more customer complaints signaling that quality is
>going down.
> can you throw some clarification on the following?
>* what are the organizational pre requisites to start the
> six sigma process?
>* is there any guide book that is practical and
>implementation oriented?
>* what role training should play in propagating six sigma
>Thanks &regards
>Senior Deputy General Manager(BPR)
>CHENNAI-600 089

BPR is an interesting phenomenon. It is a powerful technique, but if not implement by including those you are being BPR'd, chaos can result, since bad feelings can be generated in the whole organization. But I stray:

"However we have not improved the quality management process. Of late we have started getting more customer complaints signaling that quality is going down."

With this statement, my take is that you BPR'd some processes, but never looked at how management works. If you change the processes, but management doesn't change they way they manage, that can lead to a lot of trouble. The new process may rely on a certain level of autonomy, and reduced cycle times. If management doesn't adjust to that, you just get into trouble at a reduced cycle time. In this aspect, I would focus management on having proper measures (unbiased by politics), reviewed periodically (monthly is good), and action plans to close gaps. This is essentially a page from Demings PDCA (Plan-Do-Check-Act cycle for improvement).

"can you throw some clarification on the following? * what are the organizational pre requisites to start the six sigma process?"

The prerequisites are the same for any other type of systematic process improvement effort; *management understand of the changes that the new system will require *management leadership in implementing the change *unwaivering support when the road gets a little bumpy during the change *a focus on the process and achievable results, early wins help in the change process

"* is there any guide book that is practical and implementation oriented?"

I am currently not aware of a book, though I think some are in the offering. Motorola University has some books that may help. I would check with Amazon and check their offerings too. I would also review any and all books on change management. "The TEAM Handbook" by Peter Scholtes is a good implementation tools and a good overview.

"* what role training should play in propagating six sigma movement?"

It is absolutely vital. GE trains all managers who want to pursue a promotion and career with the company. They have three levels of training for their managers. One is "Black Belts" who receive extensive training (4 months of classroom and practical) and implementation experience. They have a 2 yr tour as a Black Belt and then move into a managers position and are expected to use what they learned in their new position. The other two levels are variations of OJT (On the Job Training).

The current practice is to train a select few for implementation and used them in a dedicated role to improve the business and train others in the methodology.

I hope this helps.

P.S. - In western culture, the last name is the family name, so to be formal and proper, the address would read Mr. Drensek, the informal would be Robert, but I usually go by Bob.

Robert Drensek, CQE, CQA, CRE, CMI
Quality Engineer

Don Winton

Good post!

Although I cannot recommend any of the titles (I have not read them), a lot of six sigma publications can be found at:

***DEAD LINK REMOVED*** - Link was:


Just the ramblings of an Old Wizard Warrior.
Last edited by a moderator:


One could achieve 100 sigma, (that's lots more sigmas than 6!), yet if the product you are producing cannot tolerate temperature changes, for example, then you will quickly be out of business. This is but one of the many flaws in this compilation of management, and statistical tools.

I have found the six sigma program to be a repackaged set of tools that did not work very will the first time around, and not likely to work the second. Mostly devoid of engineering and cost considerations, I find it problematic for use in hi-tech industry.


Six Sigma

An article in the recent (winter) issue of "Automotive Excellence" concerning Six sigma states that 3 sigma produces 66,807 defects per million.
I'm confused, I always thought 3 sigma was approximately 2700 PPM. Is there a different way of selecting these figures, or was I just wrong all this time?

Don Winton

It would appear the author was referring to +/- 1.5 sigma, not +/- 3 sigma. Of course, I could be wrong.



Scibilia Bruno

I have recently been visiting a GE plastics plant in the Netherlands. My impression was that ‘six sigma' there, has more to do with continuous improvement, setting hard-to-achieve objectives and team leadership than with statistical techniques.
The capability indices (Cp, Cpk, Cpm) already provide effective metrics to assess a process performance.
Six Sigma assumes that the process deviates by 1.5 sigma (sigma is the standard deviation) from the desired value. Therefore Six Sigma corresponds to a Cp of 2, a Cpk of 1.5 and a Cpm of 1.11. The reason why Six Sigma does not perform so well in terms of Cpm is that, Cpm (rightly) gives a greater weight to the bias component from the desired value (1.5 sigma).
When Six Sigma is used as a quality measure, much effort is likely to be spent trying to reduce the process variance (so that the standard deviation represents only one twelwth of the specification interval) whereas adjusting the process to the desired value would often be a more effective and less expensive strategy. This is even truer when the response is autocorrelated (which often happens in practice) and the process needs to be be continuously adjusted.
To reduce quality losses, one should first adjust and monitor the process using Statistical Process Control or Engineering Process control to ensure that the bias is eliminated.

Cp = (USL - LSL) / 6 sigma
where USL is the upper specification limit
and LSL is the lower specification limit
Sigma is the standard deviation

Cpk = Min {([USL - m]/3 sigma),([m - LSL]/3 sigma)}
where m is the average

Cpm = (USL - LSL) / [6(sigma²+(T-m)²)**0.5]
where T is the desired value

Nota bene : Please note that **0.5 means square root. I cannot convey the square root symbol.
Top Bottom