Archive for the ‘Introduction to Six Sigma’ Category

Where Do Those Six Sigma Statistics Come From?

Friday, January 13th, 2012

A student of mine had numerous questions about the various statistics used in Six Sigma. Here is my response to him in an open email:

The questions you are asking regarding “Where do these statistics come from?” require entire courses in statistics to answer. In Lean Six Sigma we take information from a dozen or so statistics courses, project management courses, psychology courses, business courses, mathematics courses, etc. and put it into an action framework that can be used to make fast improvements. We probably present less than 10% of the information you would receive if you sat through all of these courses, but we do so in less than 5% of the time it would take to complete all of these courses. It’s a tradeoff. We make the greatest compromises in the field of statistics. We discuss the use and interpretation of a select subset of statistics, and answer the question “where do these statistics come from?” by saying “they come from computer software.” While most are satisfied with this answer, some find the answer to be most unsatisfying. Judging from your questions, I suspect you are in the latter group.

anova-table-calculations-e-handbook-of-statistics

Two-Way ANOVA Calculations from E-Handbook of Statistics

Assuming you don’t have the time or the desire to take all of the courses relating to the Lean Six Sigma body of knowledge, but still seek answers to the specific statistics you asked about, I recommend the E-Handbook of Statistical Methods. This reference source is free and very comprehensive. It’s easy to search and will give you the answers you seek. For example, I searched on the term sum of squares, which you asked about, and the search returned pages on the half-normal probability plot (your question about fig. 10.26,) 1-way ANOVA (several of your question were about these calculations,) and several other related topics. A search on ss interaction provides answers to your question about the calculation of this intermediate statistic.

Sorry I can’t address all of your questions via email, but perhaps the reference above will start you on your way to answers. I had the same questions when I started learning about quality improvement nearly 45 years ago, and I am still looking for answers to questions today. Have fun!

Tom Pyzdek

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Gaming the Metrics

Tuesday, January 3rd, 2012

One of the cornerstones of quality and Lean Six Sigma is data. We insist on it. Don’t tell us what you think the situation is, let the data do the talking. In god we trust, all others bring data. You get the idea.

Die imageAn unfortunate side effect of this emphasis is the proliferation of useless data. If the useless data weren’t used then collecting the data would merely be a waste of time. But if a person’s performance is being measured by this data, you can bet your last euro that the measurements will get a lot of attention, and it will drive a lot of behavior. And if the system doesn’t change, there’s still one way to make the measurements look better: cheat.

I often open my face-to-face training sessions with Dr. Deming’s Red Bead Experiment. It’s a great icebreaker and it introduces some important statistical ideas. The experiment is actually a game with very simple rules. “Willing Workers” are required to use a paddle with holes in it to sample beads from a container which has red and white beads in it. “We don’t want any red beads.” The workers are told. To drive the point home there are Quality Inspectors to check the samples for the unwanted red beads and to record the results, and Supervisors to use the results to “coach” and discipline the hapless Willing Workers. Before the game concludes there are always participants who, seeing a bunch of red beads on their paddle, quickly dump the sample back before the count can be made. Others deliberately pick out red beads and throw them back. Still others bring partially filled paddles to the Quality Inspectors. There are all manners of ways to try and beat the system. And this is just a fun game, played for no stakes at all. Imagine what people do when real consequences are on the line, such as pay and promotions.

The most serious games are probably paid in totalitarian countries where factory managers are measured and sometimes executed when the results are less than required by the authorities. According to the UK History Learning Site in Stalin’s Russia

Factories took to inflating their production figures and the products produced were frequently so poor that they could not be used even if the factory producing those goods appeared to be meeting its target. The punishment for failure was severe. 

In the book Eat the Rich author P.J. O’Rourke tells us that in the USSR

The trouble wasn’t that factory managers disobeyed orders. The trouble was that they obeyed them precisely. If a shoe factory was told to produce 1000 shoes, it produced 1000 baby shoes because they were the cheapest and easiest to make. If it was told to produce 1000 mens shoes, it made them all one size. If it was told to produce 1000 shoes in a variety for men, women and children, it produced 998 baby shoes, one pump and a wing tip. If it was told to produce 3000 pounds of shoes it produced one enormous pair of concrete sneakers.

Perhaps P.J. is exaggerating, but the point is still essentially valid: metrics can–and probably will–be gamed. In Lean Six Sigma there’s a common metric gaming activity which I call Denominator Improvement. One of the most popular metrics is defects per million opportunities, or DPMOs. The formula itself is quite simple: DPMO = 1,000,000 x Defects/Opportunities. If someone’s performance is being measured using DPMOs they can make the metric look better by reducing defects (the numerator,) or by increasing the number of opportunities (the denominator.) For example, we might be interested in the number of typing errors in this post. The DPMO metric might be 1,000,000 x Errors/Total Words. But if this number didn’t look good enough I might also use 1,000,000 x Errors/Total Letters or 1,000,000 x Errors/Total Characters, counting spaces and punctuation.

The solution to metrics gaming is to use metrics to guide improvement, not to measure the performance of people. Metrics should be limited to those numbers that quantify an important outcome (Y metrics,) or quantify an input that is critical to the quality of the outcome (a CTQ or X metric.) The reason for quantifying these things is to discover, validate, and use a transfer function — Y=f(x), a model of the cause-and-effect relationship — to guide improvement planning and activity. When metrics serve a useful purpose such as this the tendency to manipulate and game them is, if not eliminated, at least reduced.

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The Lean, Six Sigma, and Quality Triad

Tuesday, May 31st, 2011

In response to a message from a colleague asking about the relationship between Lean, Six Sigma and Quality, I wrote the following:

Both Lean and Six Sigma (and Lean Six Sigma, the combination of the two) are ways of improving operational excellence. Lean does this by improving flow through value streams, primarily focusing on the elimination of various forms of muda (waste.) Six Sigma does this by identifying what customers and other stakeholders want and delivering it with minimal waste, variation and errors.

The Lean and Six Sigma DMAIC disciplines focus on the processes for creating and delivering products and services that meet or exceed customer expectations. The Design for Six Sigma discipline focuses on the design of products or services that meet or exceed customer expectations. Quality is a discipline which focuses on identifying customer requirements and expectations, translating them into internal requirements, and assuring that the requirements are consistently met. Of course, these Quality activities provide input into both Lean and Six Sigma. It is the “Y” being solved for when waste is identified (Lean) or when searching for the root causes of waste, variation and errors (Six Sigma.)

Thus, Lean, Quality, and Six Sigma are all different aspects of excellence.

I welcome your comments on how you consider the three areas to be related. Or do you consider them to be unrelated ideas?

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The Dirty Dozen Quality Challenges

Monday, April 18th, 2011

Lean, Six Sigma and Quality provide a set of tools and a framework for achieving excellence in any process.Quality professionals are able to help organizations determine if customer requirements are properly defined and if the organzation is meeting those requirements. Lean practitioners have a set of skills that can be used to eliminate waste in the way things are done. Six Sigma can drive variation and errors out of processes. For the sake of discussion, let’s call these the “Process Excellence Professions.” By applying these methodologies in the manufacturing arena over the past five decades the Lean, Six Sigma and Quality professions have helped increase productivity many fold, while driving errors and quality problems to levels so low that society has begun to believe that it is possible to produce risk-free products, an illusion that previous generations could not even conceive. These days when I tour manufacturing facilities around the world I find that they are able to consistently produce high quality at a very low cost per unit with very little waste.

Question: why doesn’t everyone use these tools?

Frankly, it is depressing when I leave the factory and re-enter the real world. There I encounter poor service, rampant inefficiency, horrible quality, and an attitude that this state of affairs is the best anyone can do. I believe that those working in the Process Excellence professions need to do a little soul-searching to discover the reasons why so many non-manufacturing organizations continue to ignore what we know to be valuable and highly effective frameworks, tools, and techniques for reducing variation and driving out waste and errors. In no particular order, here’s a list of things that I think contribute to the problem:

  1. The priesthood of job titles. Engineers belong in factories and laboratories. Black Belts and Green Belts belong in the dojo. Service, transactional and other businesses are put off by the names we give to people who apply Process Excellence principles. While I’m loathe to advocate adding more job titles, the existing choices may never feel quite right to people working in hospitals and banks.
  2. The jargon. DMAIC, CQTs, or SIPOCs anyone? We could do with a bit less of this alphabet soup.
  3. The time it takes to become trained. My online Lean Six Sigma Black Belt course takes 180 hours to complete. Quite a commitment for a working professional. I don’t advocate cutting content to satisfy an arbitrary time requirement, but I think it’s only fair to acknowledge that we are asking a lot.
  4. The time it takes to become proficient. Once training is complete, it takes another year or so for the practitioner to become reasonably comfortable actually using the new knowledge. Probably unavoidable, but another barrier to be sure.
  5. Charlatans and hacks. The Process Excellence profession is new and poorly defined, leaving us wide open for wannabes who are looking for the quick buck. This situation is slowly being remedied, but there are currently plenty of pretenders who need to be drummed out of the field.
  6. The lack of a standardized body of knowledge. While most experienced practitioners agree on a “starter set” of subjects that need to be covered, there is still plenty of disagreement around the edges. As evidence I point to the fact that some Six Sigma Black Belt training programs are two weeks duration, while others are six weeks. What’s up with that?
  7. The lack of a central accreditation body. Logically, ASQ could have served this purpose at one time. However, they chose the path of being a training provider instead, making them competitors to all other training providers. It’s tough to be objective when you are evaluating your competitor. The new International Association for Six Sigma Accreditation (IASSC) and their partner PEOPLECERT have stepped up to provide this service. However, the program is new and the number of accredited training organizations, curriculum providers, and trainers is still extremely limited. I’m proud to say that The Pyzdek Institute is IASSC accredited and hope others will join us.
  8. The historical origins of Process Excellence. The historical roots of our profession are in agriculture and manufacturing. The language we use reflects these origins. This will continue to impede adoption by services, healthcare, and transactional industries. By the way, it’s no accident that agriculture and manufacturing are among the most efficient and advanced sectors of the economy.
  9. The math. Math provides us with rigorous tools to quantify goals and progress, calculate costs and benefits, establish cause and effect, model our solutions before deploying them, and to do many other things. Process Excellence without math is inconceivable. Still, many fear mathematics and are put off by it. This is especially so in America, where public education does a poor job of preparing people for the study of math at the college level. We need to do more to help break down this barrier and open the door for our colleagues in non-manufacturing sectors.
  10. The mixture of soft skills and technical skills. Process Excellence requires a special mix of skills. The technical skills needed are obvious: math, statistics, etc.. But we also need to understand people skills to deal effectively with customers, team members, leaders, and stakeholders. Project management skills are a must. The ability to do preliminary financial analysis is also a requirement. It’s challenging to find someone able to deal with all of these different subjects.
  11. The arrogance of practitioners. While it’s okay to hold your head high when you earn your Professional Excellence credential, you must be careful not to flaunt your new status. Such attitudes are a turn-off to others.
  12. The added bureaucracy. Lean, Six Sigma, and Quality efforts require central organizations to get started. Ideally as Process Excellence gets into the organization’s DNA, the attitudes and knowledge of others in the rest of the organization will lead to the new bureaucracies shrinking in size over time. However, sometimes bureaucracies can take on a life of their own, sapping resources that would be better used elsewhere. Organizations that haven’t yet embarked on their own Process Excellence journey may well be wary of beginning if they hear one of these horror stories.

I’m sure that I’ve only scratched the surface here and I welcome your ideas. l’d also like to see suggestions for overcoming these obstacles to more widespread adoption of Process Excellence. Let’s see if we can help ourselves by helping non-manufacturing organizations learn to improve themselves more quickly.

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Subjective Probability of Project Success

Thursday, February 10th, 2011

One of the early lessons in all of our courses asks students to enter a number for the “subjective probability of success” for the project. Several students enter a 1 in this worksheet cell. This indicates that they believe that the project is certain to succeed. In the real world, this is extremely unlikely. Considering all of the possible ways a project might fail, a number in the 90%+ range is so optimistic as to be wishful thinking. I’ve seen so many project fail due to reasons that might have been anticipated and acted on. Looking at a project through rose-colored glasses doesn’t do anyone any favors. The best time to take a cold, hard look at any project is before it has begun. Doing so will save innumerable headaches down the road.

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The value of certification

Monday, October 25th, 2010

While I agree that the martial arts terminology is unfortunate and even a bit silly, I also believe that professional recognition serves an important purpose. If the certification is rigorous (a big if, I admit,) then it signals mastery of a well-defined body of knowledge to prospective employers. The employers can then validate the certification with interview questions, their own proctored tests, project completion requirements within their own organization, etc.. But without the initial certification credential it’s difficult for the professional to describe their level of proficiency, and equally difficult for employers to assess the job candidate.

I’ve just finished reviewing a draft ISO standard on Six Sigma which, I believe, does a good job of defining the body of knowledge and curricula for Green Belt and Black Belt training. This is an important first step, and long overdue. Of course, the questions of training, testing, project completion and certification remain to be answered. I don’t think any third-party organization will ever be able to remove the responsibility of the student and the employer for carefully researching various training and certification providers and making an informed choice on their own.

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Six Sigma Project Presentations in a Nutshell

Saturday, August 14th, 2010

I’ve reviewed thousands of improvement projects. I’ve lost count of how many project presentations I’ve attended, either for certification purposes or for presentations to leaders. I’ve come to the conclusion that most Green Belts and Black Belts simultaneously present too much information, and not enough information. If I may speak to Green Belts and Black Belts on behalf of leaders and Master Black Belts everywhere, here’s what I’d like to say. What we’re asking is actually very simple, namely how did you apply the Six Sigma process to pursue a real opportunity? In other words, for your project just walk us through the L1 Six Sigma process shown in the figure, and do so in 45 minutes or less. I actually don’t even care if you use a PowerPoint template, or even if you have any slides whatever. I just want to hear a great Six Sigma success story.

Six Sigma L1 Map

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Lean, Six Sigma, and Lean Six Sigma Elevator Speech

Friday, February 5th, 2010

I teach that by itself Lean is a way to redesign a value stream according to certain principles to improve flow in a value stream, thereby reducing cycle time and achieving a number of other benefits quickly. Six Sigma has two modes: project and operational. The project mode involves a framework such as DMAIC or DfSS. The operational mode employs Six Sigma principles (management by facts and data, statistical thinking, systematic identification of root causes of outcomes, etc.) to achieve stakeholder goals. Lean Six Sigma can be used to provide a framework for kaizen bursts, or to solve other problems preventing continuous flow in an organization or value stream.

Hmmm…Upon re-reading this it strikes me that it’s full of jargon. Let’s try putting it into layman’s terms.

Lean helps you make things with minimal waste and delay. Six Sigma helps you find out why things vary and how to reduce variation. Lean Six Sigma helps you solve challenging problems causing waste and delay.

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Business Profits Radio Interview Podcast

Tuesday, January 5th, 2010

Developing a great lifestyle from your business depends on your ability to create automatic systems to get work done without your day-to-day attention.  This program gives you a step-by-step process for creating effective business systems that allow you to automate your business.  In this podcast Business Profits Radio host Robert Skrob asks Tom about Six Sigma. What is it? How is it useful to small businesses? Can it be used to improve sales, marketing, operations? This wide-ranging interview covers a tremendous variety of topics relating to business process excellence.

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Lean Six Sigma Lives On After It Disappears

Monday, October 12th, 2009

A while ago I was asked by a colleague to recommend a Lean Six Sigma benchmark partner for a large aerospace firm that had been using Six Sigma for quite some time. Upon calling some of my favorite clients I learned that their Lean Six Sigma initiatives had been phased out. I was dismayed to hear of this and arranged to meet with one of the senior leaders to discuss why this had occurred in his organization. I learned that what had disappeared was not the Lean Six Sigma approach. Indeed, the senior leader said he knew of no other way to manage his operations. What had gone was the Lean Six Sigma bureaucracy. The personnel devoted to coaching senior leaders, providing Lean Six Sigma courses for training, etc. were gone.
It doesn’t take a lot of thought to understand why this would occur. Lean Six Sigma has been around in one form or another since 1986. That’s a pretty long run. It has evolved into a complete system for leading organizations to operational excellence. If an organization is still using Lean Six Sigma solely to execute projects, then it is missing the benefit to be had from applying the approach in its normal day-to-day operations.
If the organization has been using Lean Six Sigma for several years, it is also wasting a lot of talent by relying too much on Belts. The nature of Lean Six Sigma’s change agent infrastructure is such that the personnel involved in the program full time are routinely cycled back into the organization. These people are “damaged goods” in the sense that they can no longer function as traditional managers. Lean Six Sigma is based on principles such as root cause identification, value flow, defect prevention, etc.. Traditional management is based on command-and-control, not process; it focuses on results, not on causes. Traditional managers manage via feedback, Lean Six Sigma Leaders manage using feed-forward models.
In short, Lean Six Sigma is at its best after it has all but disappeared from the organization chart. It is still there, embedded in everything the organization is doing in its operations. It won’t go away because its practitioners realize that old-fashioned management is horribly flawed and a terrible way to run an organization. Traditional management is a disease; the Lean Six Sigma approach, done properly, is the cure.

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