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== Methodology ==
== Methodology ==
Six Sigma has two key methodologies:<ref name="juran">Joseph A. De Feo & William W Barnard. ''JURAN Institute's Six Sigma Breakthrough and Beyond - Quality Performance Breakthrough Methods'', Tata McGraw-Hill Publishing Company Limited, 2005. ISBN 0-07-059881-9</ref> DMAIC and DMADV, both inspired by [[W. Edwards Deming]]'s [[Plan-Do-Check-Act Cycle]]: DMAIC is used to improve an existing business process, and DMADV is used to create new product or process designs for predictable, defect-free performance.
Six Sigma has two key methodologies:<ref name="juran">Joseph A. De Feo & William W Barnard. ''JURAN Institute's Six Sigma Breakthrough and Beyond - Quality Performance Breakthrough Methods'', Tata McGraw-Hill Publishing Company Limited, 2005. ISBN 0-07-059881-9</ref> waffle and more waffle, both inspired by [[W. Edwards Deming]]'s [[Plan-Do-Check-Act Cycle]]: DMAIC is used to improve an existing business process, and DMADV is used to create new product or process designs for predictable, defect-free performance.


===DMAIC===
===DMAIC===

Revision as of 20:50, 7 April 2008

Not to be confused with Sigma 6.
The often-used six sigma symbol.

Six Sigma is a set of practices originally developed by Motorola to systematically improve processes by eliminating defects.[1] A defect is defined as nonconformity of a product or service to its specifications.

While the particulars of the methodology were originally formulated by Bill Smith at Motorola in 1986,[2] Six Sigma was heavily inspired by six preceding decades of quality improvement methodologies such as quality control, TQM, and Zero Defects. Like its predecessors, Six Sigma asserts the following:

  • Continuous efforts to reduce variation in process outputs is key to business success
  • Manufacturing and business processes can be measured, analyzed, improved and controlled
  • Succeeding at achieving sustained quality improvement requires commitment from the entire organization, particularly from top-level management

The term "Six Sigma" refers to the ability of highly capable processes to produce output within specification. In particular, processes that operate with six sigma quality produce at defect levels below 3.4 defects per (one) million opportunities (DPMO).[3] Six Sigma's implicit goal is to improve all processes to that level of quality or better.

Six Sigma is a registered service mark and trademark of Motorola, Inc.[4] Motorola has reported over US$17 billion in savings[5] from Six Sigma as of 2006.

In addition to Motorola, companies that adopted Six Sigma methodologies early on and continue to practice them today include Honeywell International (previously known as Allied Signal) and General Electric (introduced by Jack Welch).

Methodology

Six Sigma has two key methodologies:[6] waffle and more waffle, both inspired by W. Edwards Deming's Plan-Do-Check-Act Cycle: DMAIC is used to improve an existing business process, and DMADV is used to create new product or process designs for predictable, defect-free performance.

DMAIC

Basic methodology consists of the following five steps:

  • Define the process improvement goals that are consistent with customer demands and enterprise strategy.
  • Measure the current process and collect relevant data for future comparison.
  • Analyze to verify relationship and causality of factors. Determine what the relationship is, and attempt to ensure that all factors have been considered.
  • Improve or optimize the process based upon the analysis using techniques like Design of Experiments.
  • Control to ensure that any variances are corrected before they result in defects. Set up pilot runs to establish process capability, transition to production and thereafter continuously measure the process and institute control mechanisms.

DMADV

Basic methodology consists of the following five steps:

  • Define the goals of the design activity that are consistent with customer demands and enterprise strategy.
  • Measure and identify CTQs (critical to qualities), product capabilities, production process capability, and risk assessments.
  • Analyze to develop and design alternatives, create high-level design and evaluate design capability to select the best design.
  • Design details, optimize the design, and plan for design verification. This phase may require simulations.
  • Verify the design, set up pilot runs, implement production process and handover to process owners.

Some people have used DMAICR (Realize). Others contend that focusing on the financial gains realized through Six Sigma is counter-productive and that said financial gains are simply byproducts of a good process improvement.

Other Design for Six Sigma methodologies

Six Sigma as applied to product and process design has spawned an alphabet soup of alternatives to DMADV. Notable examples include:

Methodology Proponent
CDOC (Conceptualize, Design, Optimize, Control) SBTI
DCCDI (Define, Customer Concept, Design and Implement) Geoff Tennant
DCDOV* (Define, Concept, Design, Optimize, Verify) *derived from SBTI CDOC roadmap[7] Uniworld
D-IDOV-M (Define, Identify, Design, Optimize, Verify, Monitor)
DMADOV (Define, Measure, Analyze, Design, Optimize and Verify) General Electric
DMAI2C (Define, Measure, Analyze, Improve, Implement,Control) Cintas Corp., National Australia Group Europe
DMEDI (Define, Measure, Explore, Develop and Implement) PricewaterhouseCoopers
IDOV (Identify, Design, Optimize and Validate)
I2DOV (Invent, Innovate, Develop, Optimize, Validate)
MEDIC (Map & Measure, Explore & Evaluate, Define & Describe, Implement & Improve, Control & Conform) Philips
VCPCIA (Visualize, Commit, Prioritize, Characterize, Improve, Achieve) Raytheon

Statistics and robustness

The core of the Six Sigma methodology is a data-driven, systematic approach to problem solving, with a focus on customer impact. Statistical tools and analysis are often useful in the process. However, it is a mistake to view the core of the Six Sigma methodology as statistics; an acceptable Six Sigma project can be started with only rudimentary statistical tools.

Still, some professional statisticians criticize Six Sigma because practitioners have highly varied levels of understanding of the statistics involved.

Six Sigma as a problem-solving approach has traditionally been used in fields such as business, engineering, and production processes.

Implementation roles

One of the key innovations of Six Sigma is the professionalizing of quality management functions. Prior to Six Sigma, Quality Management in practice was largely relegated to the production floor and to statisticians in a separate quality department. Six Sigma borrows martial arts ranking terminology to define a hierarchy (and career path) that cuts across all business functions and a promotion path straight into the executive suite.

Six Sigma identifies several key roles for its successful implementation.[8]

  • Executive Leadership includes CEO and other key top management team members. They are responsible for setting up a vision for Six Sigma implementation. They also empower the other role holders with the freedom and resources to explore new ideas for breakthrough improvements.
  • Champions are responsible for the Six Sigma implementation across the organization in an integrated manner. The Executive Leadership draws them from the upper management. Champions also act as mentors to Black Belts. At GE this level of certification is now called "Quality Leader".
  • Master Black Belts, identified by champions, act as in-house expert coaches for the organization on Six Sigma. They devote 100% of their time to Six Sigma. They assist champions and guide Black Belts and Green Belts. Apart from the usual rigor of statistics, their time is spent on ensuring integrated deployment of Six Sigma across various functions and departments.
  • Experts This level of skill is used primarily within Aerospace and Defense Business Sectors. Experts work across company boundaries, improving services, processes, and products for their suppliers, their entire campuses, and for their customers. Raytheon Incorporated was one of the first companies to introduce Experts to their organizations. At Raytheon, Experts work not only across multiple sites, but across business divisions, incorporating lessons learned throughout the company.[citation needed]
  • Black Belts operate under Master Black Belts to apply Six Sigma methodology to specific projects. They devote 100% of their time to Six Sigma. They primarily focus on Six Sigma project execution, whereas Champions and Master Black Belts focus on identifying projects/functions for Six Sigma.
  • Green Belts are the employees who take up Six Sigma implementation along with their other job responsibilities. They operate under the guidance of Black Belts and support them in achieving the overall results.
  • Yellow Belts are employees who have been trained in Six Sigma techniques as part of a corporate-wide initiative, but have not completed a Six Sigma project and are not expected to actively engage in quality improvement activities[9].

In many recent programs, Green Belts and Black Belts are empowered to initiate, expand, and lead projects in their area of responsibility. The roles as defined above, therefore, conform to the older Mikel Harry/Richard Schroeder model, which is not universally accepted.

Origin

Bill Smith did not really "invent" Six Sigma in the 1980s; rather, he applied methodologies that had been available since the 1920s developed by luminaries like Shewhart, Deming, Juran, Ishikawa, Ohno, Shingo, Taguchi and Shainin. All tools used in Six Sigma programs are actually a subset of the Quality Engineering discipline and can be considered a part of the ASQ Certified Quality Engineer body of knowledge. The goal of Six Sigma, then, is to use the old tools in concert, for a greater effect than a sum-of-parts approach.

The use of "Black Belts" as itinerant change agents is controversial as it has created a cottage industry of training and certification. This relieves management of accountability for change; pre-Six Sigma implementations, exemplified by the Toyota Production System and Japan's industrial ascension, simply used the technical talent at hand – Design, Manufacturing and Quality Engineers, Toolmakers, Maintenance and Production workers – to optimize the processes.

The expansion of the various "Belts" to include "Green Belt", "Master Black Belt" and "Gold Belt" is commonly seen as a parallel to the various "Belt Factories" that exist in martial arts.

Origin and meaning of the term "six sigma process"

Sigma (the lower-case Greek letter σ) is used to represent standard deviation (a measure of variation) of a population. The term "six sigma process" comes from the notion that if one has six standard deviations between the mean of a process and the nearest specification limit, there will be practically no items that fail to meet the specifications.[10] This is based on the calculation method employed in a Process Capability Study, often used by quality professionals. The term "Six Sigma" has its roots in this tool.

In a Capability Study, the number of standard deviations between the process mean and the nearest specification limit is given in sigma units. As process standard deviation goes up, or the mean of the process moves away from the center of the tolerance, the Process Capability sigma number goes down, because fewer standard deviations will then fit between the mean and the nearest specification limit (see Process capability index).[10]

Experience has shown that in the long term, processes usually do not perform as well as they do in the short.[10] As a result, the number of sigmas that will fit between the process mean and the nearest specification limit is likely to drop over time, compared to an initial short-term study.[10] To account for this real-life increase in process variation over time, an empirically-based 1.5 sigma shift is introduced into the calculation.[11][10] According to this idea, a process that fits six sigmas between the process mean and the nearest specification limit in a short-term study will in the long term only fit 4.5 sigmas – either because the process mean is likely to move over time, or because the long-term standard deviation of the process is likely to be greater than that observed in the short term, or both.[10]

Hence the widely accepted definition of a six sigma process is one that produces 3.4 defective parts per million opportunities (DPMO).[12] This is based on the fact that a process that is normally distributed will have 3.4 parts per million beyond a point that is 4.5 standard deviations above or below the mean (one-sided Capability Study).[10] So the 3.4 DPMO of a "Six Sigma" process in fact corresponds to 4.5 sigmas, namely 6 sigmas minus the 1.5 sigma shift introduced to account for long-term variation.[10] This is designed to prevent overestimation of real-life process capability.[10]

Criticism

Lack of originality

Noted Quality expert Joseph Juran has criticized Six Sigma as "a basic version of quality improvement", stating that "[t]here is nothing new there."[13]

Studies that indicate negative effects caused by Six Sigma

A Fortune article stated that "of 58 large companies that have announced Six Sigma programs, 91 percent have trailed the S&P 500 since." The statement is attributed to "an analysis by Charles Holland of consulting firm Qualpro (which espouses a competing quality-improvement process)."[14] The gist of the article is that Six Sigma is effective at what it is intended to do, but that it is "narrowly designed to fix an existing process" and does not help in "coming up with new products or disruptive technologies." Many of these claims have been argued as being in error or ill-informed.[15][16]

A Business Week article says that James McNerney's introduction of Six Sigma at 3M may have had the effect of stifling creativity. It cites two Wharton School professors who say that Six Sigma leads to incremental innovation at the expense of blue-sky work.[17]

Based on arbitrary standards

While 3.4 defects per million might work well for certain products/processes, it might not be ideal for others. A pacemaker might need higher standards, for example, whereas a direct mail advertising campaign might need lower ones. The basis and justification for choosing 6 as the number of standard deviations is not clearly explained.[18]

Because of its arbitrary nature, the 1.5 sigma shift has been dismissed by Dr. Donald Wheeler as "goofy".[19]

Examples of some key tools used

Software used for Six Sigma

Main article: List of Six Sigma software packages

List of Six Sigma companies

Main article: List of Six Sigma companies

References

  1. ^ "Motorola University - What is Six Sigma?". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  2. ^ "The Inventors of Six Sigma". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  3. ^ "Motorola University Six Sigma Dictionary". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  4. ^ "Motorola Inc. - Motorola University". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  5. ^ "About Motorola University". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  6. ^ Joseph A. De Feo & William W Barnard. JURAN Institute's Six Sigma Breakthrough and Beyond - Quality Performance Breakthrough Methods, Tata McGraw-Hill Publishing Company Limited, 2005. ISBN 0-07-059881-9
  7. ^ *Stated in Acknowledgments - C.M. Creveling, J.L. Slutsky, and D. Antis, Jr. Design for Six Sigma: In Technology and Product Development, Prentice Hall, 2003. ISBN 0-13-0092231
  8. ^ Mikel Harry & Richard Schroeder. Six Sigma, Random House, Inc, 2000. ISBN 0-385-49437-8
  9. ^ "iSixSigma Dctionary". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  10. ^ a b c d e f g h i Tennant, Geoff (2001). SIX SIGMA: SPC and TQM in Manufacturing and Services. Gower Publishing, Ltd. pp. p. 25. ISBN 0566083744. {{cite book}}: |pages= has extra text (help)
  11. ^ Harry, Mikel (1988). The Nature of six sigma quality. Rolling Meadows, IL: Motorola University Press. pp. p. 25. ISBN 9781569460092. {{cite book}}: |pages= has extra text (help)
  12. ^ Tonner, Craig (2003-09-03). "Six Sigma". Retrieved 2006-11-26. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  13. ^ Scott Paton (2002-08). "Juran: A Lifetime of Quality". Quality Digest. Retrieved 2007-07-01. {{cite web}}: Check date values in: |date= (help)
  14. ^ Betsy Morris (2006-07-11). "Old rule: be lean and mean". Fortune. Retrieved 2006-11-26.
  15. ^ KAREN RICHARDSON (2007-01-07). "The 'Six Sigma' Factor for Home Depot". Wall Street Journal Online. Retrieved 2007-10-15.
  16. ^ Joe Ficalora & Joe Costello. "Wall Street Journal SBTI Rebuttal" (PDF). Sigma Breakthrough Technologies, Inc. Retrieved 2007-10-15.
  17. ^ Hindo, Brian (6). "At 3M, a struggle between efficiency and creativity". Business Week. Retrieved 2007-06-06. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help); Unknown parameter |month= ignored (help)
  18. ^ Criticisms of Six Sigma - http://www.sixsigmaway.org/criticisms-of-six-sigma.html
  19. ^ Wheeler, Donald J., Phd, The Six Sigma Practitioner's Guide to Data Analysis, p. 307, http://www.spcpress.com

See also

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