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OK, I hope that I'm taking into account everyone's comments. UtterUser wants Fortune 1000 companies, I want a reference site (at the moment iSixSigma seems like the best option), and FeralTitan wants to look beyond what google offers. For starters, how about the following links:
In addition, I'm in favor of adding TreQna.com once it grows a bit and starts providing more resources, and perhaps exchange it for iSixSigma. As of right now, iSixSigma is the best reference site I've seen (that's my opinion, but no one else has argued that a different site is better). I'm not sure what you all think of linking to sixsigmapc.com, but perhaps linking to the article index or the glossary would be ok. The problem is that there doesn't seem to be a general resources launch point. Comments? -- Spangineer (háblame) 13:26, August 3, 2005 (UTC)
I just visited treqna.com briefly. This site should clearly not be linked from this article. It has almost no content: two very short articles, and a half-finished DMAIC manual which requires registration in order to view it. If it becomes a well-known six sigma resource, it should be linked. As of now it is far below the standards for deserving a link. Rhobite 08:27, August 4, 2005 (UTC)
So are we ready to unprotect the site and make the change? -- Spangineer (háblame) 10:58, August 9, 2005 (UTC)
I have a new Six Sigma link, and I was wondering if you thought it would be worthwhile? It is a blog that contains Six Sigma news and information.
Six Sigma Blog What does everyone think, should we add it? Check it out and give me your opinion, or vote, or w/e. --
Scotsworth (
talk•
contribs) 13:12, August 23, 2005 (UTC)
Not quite sure who runs it, just think it's a good Six Sigma news/info page. Any other votes? Should we add it??? Posted by
User:Scotsworth --
Spangineer
(háblame) 19:03, September 9, 2005 (UTC)
K, looks like two people for the addition, and one against...any other votes? Posted by User:Scotsworth -- Spangineer (háblame) 19:03, September 9, 2005 (UTC)
3 For, 2 Against. Any more votes? -- Scotsworth ( talk• contribs) 11:17, September 7, 2005 (UTC)
Someone modified external links without discussion here. These links have been reveresed to the 'agreed set of links'. Please discuss any new links before adding them. FeralTitan 13:56, 12 September 2005 (UTC)
Spangineer, In reference to your inital comment in this section, I would like for someone to put up treqna.com as a resouce, the site is now better equipped than before. Thanks. FeralTitan 10:21, 13 October 2005 (UTC)
Someone modified external links without discussion here. These links have been reveresed to the 'agreed set of links'. Please discuss any new links before adding them. FeralTitan 14:49, 14 November 2005 (UTC)
There is repeated abuse by someone on the external links. The concerned party removes all links barring isixsigma. Please discuss before you edit. If this goes on, I will request the admin to lock up the external links and request for removal of isixsigma from the links. FeralTitan 20:06, 29 November 2005 (UTC)
IMHO better place for links is www.DMOZ.org -- AndriuZ 19:08, 26 March 2006 (UTC)
May I suggest a peer review of Discover 6 Sigma as a potential reference? 21:30, 12 October 2005 (GMT+05:30)
Please identify yourself and we will all chip in with our review.Thanks. FeralTitan 10:22, 13 October 2005 (UTC)
Thanks. My name is Sanjaya, the bogger who is blogging his thoughts in the above mentioned blog. sks 17:00, 13 October 2005 (GMT+05:30)
Cut from article: the bulk of the text, because it doesn't explain any "methodology".
Advocates say that six sigma can be applied wherever the control of variation is desired. In recent years, it has begun to branch out into the service industry, and in
2000,
Fort Wayne,
Indiana became the first
city to implement the program in a city
government. Some, claiming that Six Sigma's impact has not yet been fully realized, advocate an
open source approach so that the principles of Six Sigma might be more widely adopted.
In statistics, sigma refers to the standard deviation of a set of data; "six sigma", therefore, refers to six standard deviations. Mathematically, assuming that defects occur according to a standard normal distribution, this corresponds to approximately two quality failures per billion parts manufactured. In practical application of the Six Sigma methodology, however, the rate is taken to be 3.4 per million; see below. Initially, many believed that such high process reliability was impossible, and three sigmas (67,000 defects per million opportunities, or DPMO) was considered acceptable. However, market leaders have measurably reached six sigmas in numerous processes.
According to the graph of the standard normal distribution, only two billionths of the normal curve falls beyond six standard deviations, in contrast to the value of 3.4 millionths publicized by Six Sigma promoters. Confusingly, that value corresponds to precision within 4.5 standard deviations, reflecting a 1.5 standard deviation "shift". This shift is used to account for model inaccuracies, since defects in manufacturing processes do not always correspond to the normal distribution. Instead, processes tend to "drift" with time, causing the majority of error to fall on one side of the normal distribution and as a result, a higher defect rate than 3.4 DPMO if no shift were used. With Six Sigma methodology, however, if the process drifts by 1.5 standard deviations, the level of quality will remain within 3.4 DPMO.
However, the 1.5 sigma shift assumption is not without its critics. Donald J. Wheeler, a respected quality professional, labels it "goofy", arguing that it is misapplied in practice and that it is probably inaccurate anyway. Often, implementers of Six Sigma simply add 1.5 "sigmas" to their sigma calculation, transforming a 4.5 sigma process (3.4 DPMO) into a 6.0 sigma process. But this reflects a misunderstanding of the nature of the shift. If short-term data is used (data that does not reflect potential process drift), 1.5 sigmas should be subtracted from the final sigma calculation to account for the potential drift. Thus, achieving 3.4 DPMO using short term data reflects a three sigma process, not six sigma, when used to reflect the long-term failure rate. Alternatively, if long-term data is used to make the sigma calculations, the process drift will have already been accounted for, and no additions or subtractions to the sigma calculation are necessary.
The other common objection is that the choice of a shift of 1.5 sigmas is too arbitrary and probably inaccurate. Some suggest that the 1.5 sigma shift was implemented for marketing reasons, so that the program could be named Six Sigma instead of "4.5 Sigma" without setting the unrealistic goal of two defects per billion. However, according to original training material used at Motorola in 1985, the point at which a shift became detectable with a sample size of 4 was 1.5 standard deviations, suggesting that the number was not arbitrarily selected.
In practice, the principle of six standard deviations of quality between the upper and lower specification limits is often not applied with mathematical rigor. Instead, Six Sigma is seen as a methodology to generally minimize defects. It is used in this way in non-manufacturing environments, where it serves as an analogy to manufacturing processes and is not used for statistical distributions. Similarly, the frequent misuse of the 1.5 shift assumption in manufacturing processes is a reflection of a similar attitude in industrial applications as well.
Everyone with a Six Sigma program knows about the ±1.5 sigma drift of a process mean, experienced by all processes. What is claimed is that for a process manufacturing a product that is 100 ± 3 cm (97 - 103cm), over time it may drift up to 98.5 – 104.5 cm or down to 95.5 - 101.5 cm.
The ±1.5 shift was introduced by Mikel Harry, citing a paper written in 1975 by Evans, "Statistical Tolerancing: The State of the Art. Part 3. Shifts and Drifts". The paper is about tolerancing. That is how the overall error in an assembly is affected by the errors in components. Evans refers to a paper by Bender in 1962, "Benderizing Tolerances – A Simple Practical Probablity Method for Handling Tolerances for Limit Stack Ups". He looked at the classical situation with a stack of disks and how the overall error in the size of the stack, relates to errors in the individual disks. Based on "probability, approximations and experience", he suggests:
v = 1.5*SQRT(var X)
Harry then takes things a step further. Imagine a process where 5 samples are taken every half hour and plotted on a control chart. Harry considered the "instantaneous" initial 5 samples as being "short term" (Harry’s n=5) and the samples throughout the day as being "long term" (Harry’s g=50 points). Because of random variation in the first 5 points, the mean of the initial sample is different to the overall mean. Harry derived a relationship between the short term and long term capability, using the equation above, to produce a capability shift or "Z shift" of 1.5. Over time, the original meaning of "short term" and "long term" has been changed to result in "long term" drifting means.
Harry has clung tenaciously to the "1.5" but over the years, its derivation has been modified. In a recent note from Harry "We employed the value of 1.5 since no other empirical information was available at the time of reporting." In other words, 1.5 has now become an empirical rather than theoretical value. A further softening from Harry: "… the 1.5 constant would not be needed as an approximation".
Despite this, industry has fixed on the idea that it is impossible to keep processes on target. No matter what is done, process means will drift by ±1.5 sigma. In other words, suppose a process has a target value of 10.0, and control limits work out to be, say, 13.0 and 7.0. "Long term" the mean will drift to 11.5 (or 8.5), with control limits changing to 14.5 and 8.5. This is nonsense.
The simple truth is that any process where the mean changes by 1.5 sigma or any other amount, is not in statistical control. Such a change can often be detected by a trend on a control chart. A process that is not in control is not predictable. It may begin to produce defects, no matter where specification limits have been set.
World Class Quality means "On target with minimum variation" .
Six Sigma is controversial with the statistics profession. Some teachers of statistics are critical of the standard of statistical teaching found in Six Sigma materials. Others object to the idea that a single universal standard can be appropriate across all domains of application. They argue that quality standards should be set on a case-by-case basis using decision theory or cost-benefit analysis.
That kind of controversy should not be a significant issue since this is all about introducing some methodology into process management and improvement. The idea is to start an unending cycle of improvement and use of better tools on the industry day to day practices rather than to develop rocket science that cannot be daily applied. If "well used" the bottom line results and EBIT impact of the Six Sigma speaks for themselves much better than any opinion.
Supposedly there is a methodology underneath all this mud. Buried somewhere. Well, what is it? Can someone define it in 15 words? How about 60 words or 250?
Deming has his 14 points, at least. What are the key points of six sigma?
If no one answers that, I'm going to declare it to be nothing more than a buzzword. Uncle Ed 01:34, 17 October 2005 (UTC)
There have been continuous discrepancies over what content should be used. Some people see six sigma as a fad while others see it as a technology. Because there are people editing it with no training in six sigma and indeed the original poster was ‘venting’ about six sigma, it is not appropriate and continues to be abused. Links include marketing companies and other sites where yahoo.com’s emails are sent to bulk due to spamming reasons. Six Sigma is also a Trademark of Motorola Inc. and it maybe being used without permission. —Preceding unsigned comment added by 70.226.193.153 ( talk • contribs)
There have been continuous discrepancies over what content should be used. Some people see six sigma as a fad while others see it as a technology. Because there are people editing it with no training in six sigma and indeed the original poster was ‘venting’ about six sigma, it is not appropriate and continues to be abused. Links include marketing companies and other sites where yahoo.com’s emails are sent to bulk due to spamming reasons. Six Sigma is also a Trademark of Motorola Inc. and it may being used without permission. Since when can admin's delete a call for deletion without discussion?
Oh yeah and please show some manners by signing in after your post. FeralTitan 09:21, 7 December 2005 (UTC)
Hmmm...
I hope my points are clear now. Your apologies for ignorance have been accepted. If you still don't understand please feel free to discuss. Say hi to the folks at isixsigma.com! :) FeralTitan 16:08, 7 December 2005 (UTC)
Okay this needs to be cleared up.I am making no policies for wiki and I don't assume to either.
Deleting the article probably won't solve the issues discussed. I assume that many other readers will continuously try to re-establish the article with or without knowledge of this article. Recommend the flame-throwers go into arbitration, albeit on a page designed for that. Most readers coming to Wiki are looking for the info that is here. I doubt that many courts will sustain an infringement suit with what I've read here (...even in California or D.C....). Recommend giving Motorola credit where it is due - but also others where it is due. Don't throw the baby out with the bath water. Arbitrate. Peace, brothers and sisters. User:Cask05 12:04 Zulu, 8 December 2005
I know this is a) old, b) a variation of something that has been going the rounds since 1989, but it's still funny...
GE R&D Discovers New Element Dpbsmith (talk) 15:39, 8 December 2005 (UTC)
6 Sigma is good in many contexts -- BenGeyer
I would say there are probably thousands of articles that should be deleted before this one...even if Six Sigma is a "fad" (which is entirely possible--it could just be corporate America's latest trendy crap), its impact upon American business is more than significant enough for the article to be kept. I cannot think of a single good reason for deletion. Paul 16:50, 11 December 2005 (UTC)
I am shocked to see the above discussion. I agree with Paul that it should not be deleted. “Six Sigma” has helped business managers to manage their processes effectively leading to reduced variations & defects. At best (or worst) if it is a fad, it may be considered an excellent way to teach business managers some scientific and statistical management methods. I can never imagine deleting this article. I would even advocate restoring some of its old contents that were very informative. sks 21:36 (GMT+05:30) 11 December 2005
The article states that there are two levels of black belt and green belt. In my limited experience I've known of 'Master Black Belts'. Is this worthy of inclusion? dvc214 14:40, 17 January 2006 (UTC)
It's hilarious that this article doesn't meet Wikipedia's quality standards.
It was realised that zero defects and 100% quality are impossible to attain over most ventures lifespans. Show me a man who has scored 100% in every exam he has ever sat, even the genius of genius must face failure at some stage, even if it is less than 3.4 ppm. Also note 0 defects would simply meet the criteria of 6 sigma, and be a six sigma effort Mattyj1 13:10, 22 March 2006 (UTC)
User:Joshuarobertsteiner added a {{POV}} tag to the article, which refers to a discussion on the talk page, but did not start any such discussion. I don't see how the entire article can be considered non-neutral, so presumably he has a problem with some parts of it. He should explain here what he thinks the issues are... or edit the article himself to reflect a more neutral balance. I'm removing the tag, pending his comments here. Dpbsmith (talk) 13:03, 22 January 2006 (UTC)
Just wondered whether anyone has the necessary expertise to provide a definition of Lean Six Sigma (referred to often as Lean Sigma), and differentiate it from the "regular" Six Sigma? PeterBrooks 19:29, 10 February 2006 (UTC)
Is it due to non availability of a web URL to the same? If yes, here are the URLs that can be verified:
sks 04:53, 21 February 2006 (UTC)
Currently, the introduction contains information on its founder, and its original function as a defect function. However, it doesn't actively talk about the current role of Six Sigma, until the next section, Definitions.
Perhaps someone could merge those two sections, as the main introduction should say the most about the article... Kareeser| Talk! 15:25, 28 February 2006 (UTC)
I invite all you Six Sigma gurus to share the best practices for six sigma at Wiki Best Practices
Note on the Six Sigma page advises not to change any External links - have a question that not sure if it has been discussed - the 6sigma.us site is obviously a specific commercial consulting company site - why is this included? did not see a specific discussion on this link. VGarner 14:10, 14 March 2006 (UTC)
-I have removed a link which wasnt in the list of orignal links. If you had put this link up please, discuss it here to get it added. Thanks. FeralTitan 08:17, 15 March 2006 (UTC)
-Could someone from the original link discussion group (FeralTitan, Spangineer) post on this discussion page a summary of the links that are currently approved-perhaps a very quick summary of reason or policy on external links. I have tried to follow the discussion & compromise, but would like to know for sure. I may like to suggest links but not re-hash old discussions. Thank you. VGarner 18:46, 16 March 2006 (UTC)
--VGarner - I think Spangieer would be the best person to summarize the whole discussion without bias. The links that were agreed upon were
FeralTitan 08:59, 26 March 2006 (UTC)
Currently, the article "defines" Six Sigma as
But this is not a definition at all. It would apply to practically any quality program; heck, it probably fits what Taylor was doing a century ago. And the stated "objective" is utterly vacuous. What other objective would a quality program have? The definition should say clearly what distinguishes Six SIgma from its rivals. How, operationally, is Six Sigma different from ISO 9000 or TQM or [insert buzzword here]? Dpbsmith (talk) 15:28, 30 March 2006 (UTC)
Roderick A Munro
17:31, 9 April 2006 (UTC) [Roderick A Munro] I am new to working with Wikipedia, so you may have to advise me on some technique and procedure - was about to add items and then saw the note about posting items here first, so:
Might suggest that we add to External Links -
Six Sigma Forum Magazine is a reference reviewed journal with no advertising and is the largest publication dedicated to Six Sigma technical community. Yes, isixsigma has a new magazine also, but not hearing much about how well it is actually selling.
The Qualtiy Digest Magazine has for a number of years carried to most number of Six Sigma articles of any player in the field - up side is that it is free (can also search there site for six sigma article topics) - down site it too has a lot of advertising
Also: might I suggest starting a new header for:
Professional Society Six Sigma Certification Processes
This category should be for Not-For-Profit entities only (which these three are) that provide certifications for Green/Black Belts. These are the three primary ones that I am aware of, however, there may be others out there as well.
Can it please be explained where the 3.4 comes from? -- Rebroad 21:22, 2 April 2006 (UTC)
Where the "Six" might come from This may sound like a load of hooey - but here is an attempt to explain this "mystery" (from someone who agrees that there has been a lot of bull thrown around under the guise of Six Sigma - but that's another discusion) When you are actively measuring a process (working on a project) you are only seeing short-term variation - common cause variation from the process. In the real world - there is always some shift & drift in a process from special causes of variation. In the 80's and 90's Motorola (inventors of Six Sigma) determined that this "shift and drift" or Long-Term Dynamic Mean Variation from special cause variation over the long-term is usually 1.4 to 1.5 standard deviations. Therefore, if you have a process that you "observe" to behave at 2 defects per BILLION - you say it is operating at Six Sigma - but expect to see 3.4 defects per million due to this "mysterious" shift and drift. (6 minus the 1.5 special cause shift) This is how it was explained to me years ago - not sure what the current mythology is. In any event - I have found this mysterious shift and reporting issue with Six Sigma to be more hindrance than a help. Personally, I think that the original coiners felt that "Six Sigma" was a sexier term to sell than "four-point-five-sigma", or "three-point-four DPMO" and needed an obfuscated statistical explanation to explain it. VGarner 20:43, 4 April 2006 (UTC)
1.5 Sigma drift is not in any statistics book. I was hoping to give an explanation of where it is from, not a defense of the logic or statistics. After re-reading the talk page - I believe this is thoroughly covered under Why Six and the +-1.5 Sigma drift sections above. VGarner 22:54, 4 April 2006 (UTC)
Re SIGMAS. Dear Rebroad, Dpbsmith has given you already 3 sigmas (summaries) on this page, all of them correct, of how the 3.4 is derived from 4.5 sd: 3.4 parts in a million, 1 part in 3.4 million, 3400 parts in a million.
We are, of course, talking about OPPORTUNITIES, and not about parts. But as it is true that a part (such as a lose screw) can often be the cause of missed opportunities, we might as well accept parts in everyday language.
Unfortunately, Dpbsmith (like everyone else on this page) has failed to explain the SIX sigmas. So pay attention now: The bell curve has TWO sides. The three sigmas that Dpbsmith has given you refer only to the left side of it. Behind the curve is the terminus technicus. An equivalent three must be found on the right side. So there you have your SIX.--
BZ(Bruno Zollinger)
11:36, 6 April 2006 (UTC)
Here is a link from a human resources site that talks about the HR implications of the Six Sigma initiative. I put it in and noticed that there has been significant discussion on the external links on this page. Could / should I add this link:
One book, keeps showing up as reference no. 18, despite many people deleting it. Could it be an attempt to advertise the book? ramit 06:57, 14 May 2006 (UTC)
Would it be reasonable to say Six Sigma is a revival of Micromanagement? In my reading about it, it would appear that it's goal is to track as many variables as possible even if the advantage is not readily transparent?? Maybe I'm missing something,jme 66.72.215.225
Any reason why Category:Motorola was removed? I'm going to restore it. Paul 04:33, 24 May 2006 (UTC)
I have come across a website that offers more six sigma resource than any on the web and I think that it is way better that isixsigma. visit it and I am sure you will consider adding it to the list. http://www.sixsigmafirst.com/ Rodney
I wandered into this article from dabbawala and had to look below the table of contents to figure out what it is. I have reworked the lead so the definition comes before the details of who has used it or developed it. Also, does anyone else notice an unencyclopedic tone (nevertheless non-standard formatting) to this article? Less management jargon advocacy and more straightforward explanation about what it is and what it is used for would be appreciated. - BT 16:11, 13 June 2006 (UTC)
"In truth, there is very little that is new within Six Sigma. However, it does use the old tools in concert, for far greater effect. The telephone, the internal combustion engine, and the computer were all made from existing technology, used in a new way. The same is true of Six Sigma."
I feel that this passage is idiotic and removed the last two, especially unneccessary sentences, but it was reverted... why? --anon —Preceding unsigned comment added by 192.193.220.142 ( talk • contribs)
Additionally, claiming a "far greater effect" is POV given that the previous paragraph discussed criticism of six sigma's lack of originality.—Preceding unsigned comment added by 192.193.220.142 ( talk • contribs)
The anon user had made some changes which I disagree with and had reverted. He has however made the changes again. Since this is not blatant vandalism but more towards POV, I do not want to approach WP:3RR. In case anybody else agrees with me, please feel free to revert the changes. -- Lost 09:35, 27 June 2006 (UTC)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 | Archive 3 | Archive 4 | Archive 5 |
OK, I hope that I'm taking into account everyone's comments. UtterUser wants Fortune 1000 companies, I want a reference site (at the moment iSixSigma seems like the best option), and FeralTitan wants to look beyond what google offers. For starters, how about the following links:
In addition, I'm in favor of adding TreQna.com once it grows a bit and starts providing more resources, and perhaps exchange it for iSixSigma. As of right now, iSixSigma is the best reference site I've seen (that's my opinion, but no one else has argued that a different site is better). I'm not sure what you all think of linking to sixsigmapc.com, but perhaps linking to the article index or the glossary would be ok. The problem is that there doesn't seem to be a general resources launch point. Comments? -- Spangineer (háblame) 13:26, August 3, 2005 (UTC)
I just visited treqna.com briefly. This site should clearly not be linked from this article. It has almost no content: two very short articles, and a half-finished DMAIC manual which requires registration in order to view it. If it becomes a well-known six sigma resource, it should be linked. As of now it is far below the standards for deserving a link. Rhobite 08:27, August 4, 2005 (UTC)
So are we ready to unprotect the site and make the change? -- Spangineer (háblame) 10:58, August 9, 2005 (UTC)
I have a new Six Sigma link, and I was wondering if you thought it would be worthwhile? It is a blog that contains Six Sigma news and information.
Six Sigma Blog What does everyone think, should we add it? Check it out and give me your opinion, or vote, or w/e. --
Scotsworth (
talk•
contribs) 13:12, August 23, 2005 (UTC)
Not quite sure who runs it, just think it's a good Six Sigma news/info page. Any other votes? Should we add it??? Posted by
User:Scotsworth --
Spangineer
(háblame) 19:03, September 9, 2005 (UTC)
K, looks like two people for the addition, and one against...any other votes? Posted by User:Scotsworth -- Spangineer (háblame) 19:03, September 9, 2005 (UTC)
3 For, 2 Against. Any more votes? -- Scotsworth ( talk• contribs) 11:17, September 7, 2005 (UTC)
Someone modified external links without discussion here. These links have been reveresed to the 'agreed set of links'. Please discuss any new links before adding them. FeralTitan 13:56, 12 September 2005 (UTC)
Spangineer, In reference to your inital comment in this section, I would like for someone to put up treqna.com as a resouce, the site is now better equipped than before. Thanks. FeralTitan 10:21, 13 October 2005 (UTC)
Someone modified external links without discussion here. These links have been reveresed to the 'agreed set of links'. Please discuss any new links before adding them. FeralTitan 14:49, 14 November 2005 (UTC)
There is repeated abuse by someone on the external links. The concerned party removes all links barring isixsigma. Please discuss before you edit. If this goes on, I will request the admin to lock up the external links and request for removal of isixsigma from the links. FeralTitan 20:06, 29 November 2005 (UTC)
IMHO better place for links is www.DMOZ.org -- AndriuZ 19:08, 26 March 2006 (UTC)
May I suggest a peer review of Discover 6 Sigma as a potential reference? 21:30, 12 October 2005 (GMT+05:30)
Please identify yourself and we will all chip in with our review.Thanks. FeralTitan 10:22, 13 October 2005 (UTC)
Thanks. My name is Sanjaya, the bogger who is blogging his thoughts in the above mentioned blog. sks 17:00, 13 October 2005 (GMT+05:30)
Cut from article: the bulk of the text, because it doesn't explain any "methodology".
Advocates say that six sigma can be applied wherever the control of variation is desired. In recent years, it has begun to branch out into the service industry, and in
2000,
Fort Wayne,
Indiana became the first
city to implement the program in a city
government. Some, claiming that Six Sigma's impact has not yet been fully realized, advocate an
open source approach so that the principles of Six Sigma might be more widely adopted.
In statistics, sigma refers to the standard deviation of a set of data; "six sigma", therefore, refers to six standard deviations. Mathematically, assuming that defects occur according to a standard normal distribution, this corresponds to approximately two quality failures per billion parts manufactured. In practical application of the Six Sigma methodology, however, the rate is taken to be 3.4 per million; see below. Initially, many believed that such high process reliability was impossible, and three sigmas (67,000 defects per million opportunities, or DPMO) was considered acceptable. However, market leaders have measurably reached six sigmas in numerous processes.
According to the graph of the standard normal distribution, only two billionths of the normal curve falls beyond six standard deviations, in contrast to the value of 3.4 millionths publicized by Six Sigma promoters. Confusingly, that value corresponds to precision within 4.5 standard deviations, reflecting a 1.5 standard deviation "shift". This shift is used to account for model inaccuracies, since defects in manufacturing processes do not always correspond to the normal distribution. Instead, processes tend to "drift" with time, causing the majority of error to fall on one side of the normal distribution and as a result, a higher defect rate than 3.4 DPMO if no shift were used. With Six Sigma methodology, however, if the process drifts by 1.5 standard deviations, the level of quality will remain within 3.4 DPMO.
However, the 1.5 sigma shift assumption is not without its critics. Donald J. Wheeler, a respected quality professional, labels it "goofy", arguing that it is misapplied in practice and that it is probably inaccurate anyway. Often, implementers of Six Sigma simply add 1.5 "sigmas" to their sigma calculation, transforming a 4.5 sigma process (3.4 DPMO) into a 6.0 sigma process. But this reflects a misunderstanding of the nature of the shift. If short-term data is used (data that does not reflect potential process drift), 1.5 sigmas should be subtracted from the final sigma calculation to account for the potential drift. Thus, achieving 3.4 DPMO using short term data reflects a three sigma process, not six sigma, when used to reflect the long-term failure rate. Alternatively, if long-term data is used to make the sigma calculations, the process drift will have already been accounted for, and no additions or subtractions to the sigma calculation are necessary.
The other common objection is that the choice of a shift of 1.5 sigmas is too arbitrary and probably inaccurate. Some suggest that the 1.5 sigma shift was implemented for marketing reasons, so that the program could be named Six Sigma instead of "4.5 Sigma" without setting the unrealistic goal of two defects per billion. However, according to original training material used at Motorola in 1985, the point at which a shift became detectable with a sample size of 4 was 1.5 standard deviations, suggesting that the number was not arbitrarily selected.
In practice, the principle of six standard deviations of quality between the upper and lower specification limits is often not applied with mathematical rigor. Instead, Six Sigma is seen as a methodology to generally minimize defects. It is used in this way in non-manufacturing environments, where it serves as an analogy to manufacturing processes and is not used for statistical distributions. Similarly, the frequent misuse of the 1.5 shift assumption in manufacturing processes is a reflection of a similar attitude in industrial applications as well.
Everyone with a Six Sigma program knows about the ±1.5 sigma drift of a process mean, experienced by all processes. What is claimed is that for a process manufacturing a product that is 100 ± 3 cm (97 - 103cm), over time it may drift up to 98.5 – 104.5 cm or down to 95.5 - 101.5 cm.
The ±1.5 shift was introduced by Mikel Harry, citing a paper written in 1975 by Evans, "Statistical Tolerancing: The State of the Art. Part 3. Shifts and Drifts". The paper is about tolerancing. That is how the overall error in an assembly is affected by the errors in components. Evans refers to a paper by Bender in 1962, "Benderizing Tolerances – A Simple Practical Probablity Method for Handling Tolerances for Limit Stack Ups". He looked at the classical situation with a stack of disks and how the overall error in the size of the stack, relates to errors in the individual disks. Based on "probability, approximations and experience", he suggests:
v = 1.5*SQRT(var X)
Harry then takes things a step further. Imagine a process where 5 samples are taken every half hour and plotted on a control chart. Harry considered the "instantaneous" initial 5 samples as being "short term" (Harry’s n=5) and the samples throughout the day as being "long term" (Harry’s g=50 points). Because of random variation in the first 5 points, the mean of the initial sample is different to the overall mean. Harry derived a relationship between the short term and long term capability, using the equation above, to produce a capability shift or "Z shift" of 1.5. Over time, the original meaning of "short term" and "long term" has been changed to result in "long term" drifting means.
Harry has clung tenaciously to the "1.5" but over the years, its derivation has been modified. In a recent note from Harry "We employed the value of 1.5 since no other empirical information was available at the time of reporting." In other words, 1.5 has now become an empirical rather than theoretical value. A further softening from Harry: "… the 1.5 constant would not be needed as an approximation".
Despite this, industry has fixed on the idea that it is impossible to keep processes on target. No matter what is done, process means will drift by ±1.5 sigma. In other words, suppose a process has a target value of 10.0, and control limits work out to be, say, 13.0 and 7.0. "Long term" the mean will drift to 11.5 (or 8.5), with control limits changing to 14.5 and 8.5. This is nonsense.
The simple truth is that any process where the mean changes by 1.5 sigma or any other amount, is not in statistical control. Such a change can often be detected by a trend on a control chart. A process that is not in control is not predictable. It may begin to produce defects, no matter where specification limits have been set.
World Class Quality means "On target with minimum variation" .
Six Sigma is controversial with the statistics profession. Some teachers of statistics are critical of the standard of statistical teaching found in Six Sigma materials. Others object to the idea that a single universal standard can be appropriate across all domains of application. They argue that quality standards should be set on a case-by-case basis using decision theory or cost-benefit analysis.
That kind of controversy should not be a significant issue since this is all about introducing some methodology into process management and improvement. The idea is to start an unending cycle of improvement and use of better tools on the industry day to day practices rather than to develop rocket science that cannot be daily applied. If "well used" the bottom line results and EBIT impact of the Six Sigma speaks for themselves much better than any opinion.
Supposedly there is a methodology underneath all this mud. Buried somewhere. Well, what is it? Can someone define it in 15 words? How about 60 words or 250?
Deming has his 14 points, at least. What are the key points of six sigma?
If no one answers that, I'm going to declare it to be nothing more than a buzzword. Uncle Ed 01:34, 17 October 2005 (UTC)
There have been continuous discrepancies over what content should be used. Some people see six sigma as a fad while others see it as a technology. Because there are people editing it with no training in six sigma and indeed the original poster was ‘venting’ about six sigma, it is not appropriate and continues to be abused. Links include marketing companies and other sites where yahoo.com’s emails are sent to bulk due to spamming reasons. Six Sigma is also a Trademark of Motorola Inc. and it maybe being used without permission. —Preceding unsigned comment added by 70.226.193.153 ( talk • contribs)
There have been continuous discrepancies over what content should be used. Some people see six sigma as a fad while others see it as a technology. Because there are people editing it with no training in six sigma and indeed the original poster was ‘venting’ about six sigma, it is not appropriate and continues to be abused. Links include marketing companies and other sites where yahoo.com’s emails are sent to bulk due to spamming reasons. Six Sigma is also a Trademark of Motorola Inc. and it may being used without permission. Since when can admin's delete a call for deletion without discussion?
Oh yeah and please show some manners by signing in after your post. FeralTitan 09:21, 7 December 2005 (UTC)
Hmmm...
I hope my points are clear now. Your apologies for ignorance have been accepted. If you still don't understand please feel free to discuss. Say hi to the folks at isixsigma.com! :) FeralTitan 16:08, 7 December 2005 (UTC)
Okay this needs to be cleared up.I am making no policies for wiki and I don't assume to either.
Deleting the article probably won't solve the issues discussed. I assume that many other readers will continuously try to re-establish the article with or without knowledge of this article. Recommend the flame-throwers go into arbitration, albeit on a page designed for that. Most readers coming to Wiki are looking for the info that is here. I doubt that many courts will sustain an infringement suit with what I've read here (...even in California or D.C....). Recommend giving Motorola credit where it is due - but also others where it is due. Don't throw the baby out with the bath water. Arbitrate. Peace, brothers and sisters. User:Cask05 12:04 Zulu, 8 December 2005
I know this is a) old, b) a variation of something that has been going the rounds since 1989, but it's still funny...
GE R&D Discovers New Element Dpbsmith (talk) 15:39, 8 December 2005 (UTC)
6 Sigma is good in many contexts -- BenGeyer
I would say there are probably thousands of articles that should be deleted before this one...even if Six Sigma is a "fad" (which is entirely possible--it could just be corporate America's latest trendy crap), its impact upon American business is more than significant enough for the article to be kept. I cannot think of a single good reason for deletion. Paul 16:50, 11 December 2005 (UTC)
I am shocked to see the above discussion. I agree with Paul that it should not be deleted. “Six Sigma” has helped business managers to manage their processes effectively leading to reduced variations & defects. At best (or worst) if it is a fad, it may be considered an excellent way to teach business managers some scientific and statistical management methods. I can never imagine deleting this article. I would even advocate restoring some of its old contents that were very informative. sks 21:36 (GMT+05:30) 11 December 2005
The article states that there are two levels of black belt and green belt. In my limited experience I've known of 'Master Black Belts'. Is this worthy of inclusion? dvc214 14:40, 17 January 2006 (UTC)
It's hilarious that this article doesn't meet Wikipedia's quality standards.
It was realised that zero defects and 100% quality are impossible to attain over most ventures lifespans. Show me a man who has scored 100% in every exam he has ever sat, even the genius of genius must face failure at some stage, even if it is less than 3.4 ppm. Also note 0 defects would simply meet the criteria of 6 sigma, and be a six sigma effort Mattyj1 13:10, 22 March 2006 (UTC)
User:Joshuarobertsteiner added a {{POV}} tag to the article, which refers to a discussion on the talk page, but did not start any such discussion. I don't see how the entire article can be considered non-neutral, so presumably he has a problem with some parts of it. He should explain here what he thinks the issues are... or edit the article himself to reflect a more neutral balance. I'm removing the tag, pending his comments here. Dpbsmith (talk) 13:03, 22 January 2006 (UTC)
Just wondered whether anyone has the necessary expertise to provide a definition of Lean Six Sigma (referred to often as Lean Sigma), and differentiate it from the "regular" Six Sigma? PeterBrooks 19:29, 10 February 2006 (UTC)
Is it due to non availability of a web URL to the same? If yes, here are the URLs that can be verified:
sks 04:53, 21 February 2006 (UTC)
Currently, the introduction contains information on its founder, and its original function as a defect function. However, it doesn't actively talk about the current role of Six Sigma, until the next section, Definitions.
Perhaps someone could merge those two sections, as the main introduction should say the most about the article... Kareeser| Talk! 15:25, 28 February 2006 (UTC)
I invite all you Six Sigma gurus to share the best practices for six sigma at Wiki Best Practices
Note on the Six Sigma page advises not to change any External links - have a question that not sure if it has been discussed - the 6sigma.us site is obviously a specific commercial consulting company site - why is this included? did not see a specific discussion on this link. VGarner 14:10, 14 March 2006 (UTC)
-I have removed a link which wasnt in the list of orignal links. If you had put this link up please, discuss it here to get it added. Thanks. FeralTitan 08:17, 15 March 2006 (UTC)
-Could someone from the original link discussion group (FeralTitan, Spangineer) post on this discussion page a summary of the links that are currently approved-perhaps a very quick summary of reason or policy on external links. I have tried to follow the discussion & compromise, but would like to know for sure. I may like to suggest links but not re-hash old discussions. Thank you. VGarner 18:46, 16 March 2006 (UTC)
--VGarner - I think Spangieer would be the best person to summarize the whole discussion without bias. The links that were agreed upon were
FeralTitan 08:59, 26 March 2006 (UTC)
Currently, the article "defines" Six Sigma as
But this is not a definition at all. It would apply to practically any quality program; heck, it probably fits what Taylor was doing a century ago. And the stated "objective" is utterly vacuous. What other objective would a quality program have? The definition should say clearly what distinguishes Six SIgma from its rivals. How, operationally, is Six Sigma different from ISO 9000 or TQM or [insert buzzword here]? Dpbsmith (talk) 15:28, 30 March 2006 (UTC)
Roderick A Munro
17:31, 9 April 2006 (UTC) [Roderick A Munro] I am new to working with Wikipedia, so you may have to advise me on some technique and procedure - was about to add items and then saw the note about posting items here first, so:
Might suggest that we add to External Links -
Six Sigma Forum Magazine is a reference reviewed journal with no advertising and is the largest publication dedicated to Six Sigma technical community. Yes, isixsigma has a new magazine also, but not hearing much about how well it is actually selling.
The Qualtiy Digest Magazine has for a number of years carried to most number of Six Sigma articles of any player in the field - up side is that it is free (can also search there site for six sigma article topics) - down site it too has a lot of advertising
Also: might I suggest starting a new header for:
Professional Society Six Sigma Certification Processes
This category should be for Not-For-Profit entities only (which these three are) that provide certifications for Green/Black Belts. These are the three primary ones that I am aware of, however, there may be others out there as well.
Can it please be explained where the 3.4 comes from? -- Rebroad 21:22, 2 April 2006 (UTC)
Where the "Six" might come from This may sound like a load of hooey - but here is an attempt to explain this "mystery" (from someone who agrees that there has been a lot of bull thrown around under the guise of Six Sigma - but that's another discusion) When you are actively measuring a process (working on a project) you are only seeing short-term variation - common cause variation from the process. In the real world - there is always some shift & drift in a process from special causes of variation. In the 80's and 90's Motorola (inventors of Six Sigma) determined that this "shift and drift" or Long-Term Dynamic Mean Variation from special cause variation over the long-term is usually 1.4 to 1.5 standard deviations. Therefore, if you have a process that you "observe" to behave at 2 defects per BILLION - you say it is operating at Six Sigma - but expect to see 3.4 defects per million due to this "mysterious" shift and drift. (6 minus the 1.5 special cause shift) This is how it was explained to me years ago - not sure what the current mythology is. In any event - I have found this mysterious shift and reporting issue with Six Sigma to be more hindrance than a help. Personally, I think that the original coiners felt that "Six Sigma" was a sexier term to sell than "four-point-five-sigma", or "three-point-four DPMO" and needed an obfuscated statistical explanation to explain it. VGarner 20:43, 4 April 2006 (UTC)
1.5 Sigma drift is not in any statistics book. I was hoping to give an explanation of where it is from, not a defense of the logic or statistics. After re-reading the talk page - I believe this is thoroughly covered under Why Six and the +-1.5 Sigma drift sections above. VGarner 22:54, 4 April 2006 (UTC)
Re SIGMAS. Dear Rebroad, Dpbsmith has given you already 3 sigmas (summaries) on this page, all of them correct, of how the 3.4 is derived from 4.5 sd: 3.4 parts in a million, 1 part in 3.4 million, 3400 parts in a million.
We are, of course, talking about OPPORTUNITIES, and not about parts. But as it is true that a part (such as a lose screw) can often be the cause of missed opportunities, we might as well accept parts in everyday language.
Unfortunately, Dpbsmith (like everyone else on this page) has failed to explain the SIX sigmas. So pay attention now: The bell curve has TWO sides. The three sigmas that Dpbsmith has given you refer only to the left side of it. Behind the curve is the terminus technicus. An equivalent three must be found on the right side. So there you have your SIX.--
BZ(Bruno Zollinger)
11:36, 6 April 2006 (UTC)
Here is a link from a human resources site that talks about the HR implications of the Six Sigma initiative. I put it in and noticed that there has been significant discussion on the external links on this page. Could / should I add this link:
One book, keeps showing up as reference no. 18, despite many people deleting it. Could it be an attempt to advertise the book? ramit 06:57, 14 May 2006 (UTC)
Would it be reasonable to say Six Sigma is a revival of Micromanagement? In my reading about it, it would appear that it's goal is to track as many variables as possible even if the advantage is not readily transparent?? Maybe I'm missing something,jme 66.72.215.225
Any reason why Category:Motorola was removed? I'm going to restore it. Paul 04:33, 24 May 2006 (UTC)
I have come across a website that offers more six sigma resource than any on the web and I think that it is way better that isixsigma. visit it and I am sure you will consider adding it to the list. http://www.sixsigmafirst.com/ Rodney
I wandered into this article from dabbawala and had to look below the table of contents to figure out what it is. I have reworked the lead so the definition comes before the details of who has used it or developed it. Also, does anyone else notice an unencyclopedic tone (nevertheless non-standard formatting) to this article? Less management jargon advocacy and more straightforward explanation about what it is and what it is used for would be appreciated. - BT 16:11, 13 June 2006 (UTC)
"In truth, there is very little that is new within Six Sigma. However, it does use the old tools in concert, for far greater effect. The telephone, the internal combustion engine, and the computer were all made from existing technology, used in a new way. The same is true of Six Sigma."
I feel that this passage is idiotic and removed the last two, especially unneccessary sentences, but it was reverted... why? --anon —Preceding unsigned comment added by 192.193.220.142 ( talk • contribs)
Additionally, claiming a "far greater effect" is POV given that the previous paragraph discussed criticism of six sigma's lack of originality.—Preceding unsigned comment added by 192.193.220.142 ( talk • contribs)
The anon user had made some changes which I disagree with and had reverted. He has however made the changes again. Since this is not blatant vandalism but more towards POV, I do not want to approach WP:3RR. In case anybody else agrees with me, please feel free to revert the changes. -- Lost 09:35, 27 June 2006 (UTC)