Talk:Six Sigma/Archive 2

message: 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.
===Why six?===
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.
==== The ±1.5 sigma drift ====
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" .
=== Criticisms of Six Sigma ===
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.
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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)
replies: text: I've moved most of this back into the article; admittedly, we need more on the actual methodologies of Six Sigma.  Anyone want to write about the history and theory of Six Sigma's methods? --Spangineer (háblame) 03:06, 17 October 2005 (UTC)
thread_title: No content

message: 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)
replies: text: I've moved most of this back into the article; admittedly, we need more on the actual methodologies of Six Sigma.  Anyone want to write about the history and theory of Six Sigma's methods? --Spangineer (háblame) 03:06, 17 October 2005 (UTC)
thread_title:  Criticisms of Six Sigma 

message: 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)
thread_title:  Sixsigmium 

message: 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)
thread_title:  Deletion?? 

message: 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)
thread_title:  Back to content 

message: It's hilarious that this article doesn't meet Wikipedia's quality standards.
:Why? Wikipedia doesn't have any quality management leadership process methodology buzzword implementation planning process management continuous improvement system in place, so what do you expect?
:On an unrelated note: so, this decade's fad is Four-and-a-half Sigma—which for some unfathomable reason is called Six Sigma—which allows a defect rate of 1 in 3.4 million. A few decades ago the fad was Zero Defects. I have to ask: why has the bar been lowered? Why would anyone want one defect in 3.4 million when they could have Zero? Particularly when it is well known that Quality is free? Why shouldn't we demand all the free quality we can get? Dpbsmith (talk) 13:50, 19 January 2006 (UTC)
replies: text: While I agree that it's odd that that they used the name "Zero Defects" for a methodology that does not achieve zero defects, it's no stranger than using name Six Sigma for a methodology that does not in practice actually achieve a one in 3.4 million defect rate, let alone the one in a billion defect rate implied by its name. Dpbsmith (talk) 14:42, 22 March 2006 (UTC)

text: Yes! This article is evidence that Wikipedia needs to adopt Six Sigma to ensure that articles meet required quality standards. Wikipedia needs a centralized top down chain of command with certified green and black belts to authorize changes to each article. Without this kind of proper procedure and structure, the quality of the Wikipedia doomed. Doomed! Jeff Carr 23:44, 21 January 2006 (UTC)
thread_title:  The irony 

message: User:Joshuarobertsteiner added a  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)
thread_title:  <nowiki>{{POV}}</nowiki> tag 

message: 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)
thread_title:  Lean Six Sigma (Lean Sigma) 

message: Is it due to non availability of a web URL to the same? If yes, here are the URLs that can be verified:
* For Ref#08 - http://doi.ieeecomputersociety.org/10.1109/APAQ.2000.883798
* For Ref#10 - http://www.asq.org/pub/sixsigma/past/vol3_issue2/ssfmv3i2jones.pdf
sks 04:53, 21 February 2006 (UTC)
thread_title:  The template Journal reference has been proposed for deletion here 

message: 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)
thread_title:  Introduction 

message: 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)
replies: text: Good point; it was added by an anon a few days ago and I missed it. I've removed it. —Spangineer (háblame) 21:30, 14 March 2006 (UTC)

text: The first three that were agreed upon were GE, Motorola, and isixsigma.  GE & Motorola were key players in the early years of Six Sigma, and have well developed internal six sigma programs.  The other one, isixsigma.com, is a good general resource—it has large amounts of information, but on the downside, it contains alot of advertising.  The other two were more recently added.  Discover 6 Sigma is a blog, and thus offers a different feel.  It too is a good resource with alot of valuable information.  Finally, TreQna, an open source Six Sigma community project, was added once it began to grow and develop.  It offers what the others don't—a six sigma discussion area and resource area in one, all without advertising.  These five I feel cover a variety of website styles and a variety of six sigma content.  They may be could be replaced by other links in the future, and others may be added to them, but we have to be careful to prevent this from becoming a link farm.  The idea is to provide a few relevant links, and I think we've accomplished that here. —Spangineer[es] (háblame) 18:34, 26 March 2006 (UTC)
thread_title:  External Links Question 

message: Currently, the article "defines" Six Sigma as
:a methodology to manage process variations that cause defects, defined as unacceptable deviation from the mean or target; and to systematically work towards managing variation to eliminate those defects[6]. The objective of Six Sigma is to deliver world-class performance, reliability, and value to the end customer.
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)
replies: text: I'd be OK with adding the Six Sigma Forum Magazine link, and the first two of the certification processes links.  Not sure about the other two.  The advertising of the Quality Digest Magazine is rather annoying, but we do link to isixsigma, which is pretty heavy in advertising.  Also, how established is the IABLS?  I'd rather link only to the major players rather than attempting to link to every non-profit who offers a six sigma certificate.  If we do add the three I suggest, it might be a good idea to remove the Discover6Sigma link (since its information is probably largely repeated). --Spangineer[es] (háblame) 15:49, 8 May 2006 (UTC)
thread_title:  Problem with the "definition" 

message: 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)
thread_title: The Question is: Where do the ''parts'' come from?

message: 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:
*Role of HR in the Six Sigma Initiative
:Is there more material somewhere, or is this the only relevant page? I think more information is necessary to warrant a link on this article. --Spangineer[es] (háblame) 15:42, 8 May 2006 (UTC)
thread_title:  Do You Think That a Link from H R Professor is relevant? 

message: 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)
replies: text: Slocum1946 and BezLocu - Please see the Three revert rule on the Wikipedia policy. Secondly, I also advise you to go through the Wikipedia style guide on what the References section may or may not contain. Please do not keep adding or deleting in this section ramit 12:59, 22 May 2006 (UTC)
replies: text:  , pls dont go on adding the book written by you to Six Sigma. Please list it on the talk page and try to build consensus around it. There are many editors who have helped in building this page. Please respect their views. Lost 18:26, 27 May 2006 (UTC)
thread_title:  References 

message: 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,jme66.72.215.225
: I dont think so... I find it a very structured way to fix things. Especially in areas where there should be a process, such as SCM, manufacturing, finance, operations, etc, it faciilitates one very well.. ramit 18:53, 15 May 2006 (UTC)
thread_title:  Micromanagement? 

message: Any reason why Category:Motorola was removed? I'm going to restore it. Paul 04:33, 24 May 2006 (UTC)
replies: text: Hi there... Do u think we should add Category:General Electric too? Lost 05:07, 24 May 2006 (UTC)
thread_title:  Category 

message: 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
:Thank you. Will go through it and give my comments.. -- Lost 17:59, 8 June 2006 (UTC)
thread_title:  External link suggestion 

message: 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)
thread_title:  reworking of lead 

message: 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)
thread_title:  Edits by [[user:70.215.251.48]]