The often-used six sigma symbol.
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Six Sigma is a business management strategy, originally developed by Motorola, that today enjoys wide-spread application in many sectors of industry. For other uses of this term see Industry (disambiguation An industry (from Latin industrius, "diligent industrious" The primary characteristic of batch production is that all components are completed at a workstation before they move to the next one Continuous production is a method used to manufacture, produce or process materials without interruption Job production involves producing a one-off product for a specific customer Lean manufacturing or lean production, which is often known simply as " Lean " is the practice of a theory of production that considers the expenditure Total Productive Maintenance is a new way of looking at maintenance or conversely a reversion to old ways but on a mass scale Theory of Constraints (TOC is an overall Management philosophy. Reliability-Centered Maintenance, often known as RCM, is an industrial improvement approach focused on identifying and establishing the operational maintenance and capital S88, shorthand for ANSI/ISA-88, is a standard addressing batch process control ANSI/ISA-95, or ISA-95 as it is more commonly referred is an International standard for developing an automated interface between enterprise and control systems Enterprise resource planning ( ERP) is the planning of how business resources (materials employees customers etc IEC 62264 is a International standard for Enterprise-control system integration B2MML or Business To Manufacturing Markup Language is an XML implementation of the ANSI/ ISA -95 family of standards ( ISA-95) known internationally A programmable logic controller ( PLC) or programmable controller is a Digital computer used for Automation of industrial processes such as A distributed control system (DCS refers to a Control system usually of a Manufacturing system, Process or any kind of Dynamic system, Management (covering theory practice and scope of management and Manager' (covering the people who manage might help clarify and systematise Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois.

Six Sigma seeks to identify and remove the causes of defects and errors in manufacturing and business processes. Manufacturing (from Latin manu factura, "making by hand" is the use of tools and labor to make things for use or sale A business process or business method is a collection of interrelated Tasks, which accomplish a particular goal [1] It uses a set of quality management methods, including statistical methods, and creates a special infrastructure of people within the organization ("Black Belts" etc. Quality management is a method for ensuring that all the activities necessary to design develop and implement a product or service are effective and efficient with respect to the system Statistics is a mathematical science pertaining to the collection analysis interpretation or explanation and presentation of Data. ) who are experts in these methods. [1] Each Six Sigma project carried out within an organization follows a defined sequence of steps and has quantified financial targets (cost reduction or profit increase). [1]

Historical overview

Six Sigma was originally developed as a set of practices designed to improve manufacturing processes and eliminate defects, but its application was subsequently extended to other types of business processes as well. Industrial processes are procedures involving chemical or mechanical steps to aid in the Manufacture of an item or items usually carried out on a very [2] In Six Sigma, a defect is defined as anything that could lead to customer dissatisfaction. [1]

The particulars of the methodology were first formulated by Bill Smith at Motorola in 1986. Bill Smith (1929 - 1993 is the " Father of Six Sigma " Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. [3] Six Sigma was heavily inspired by six preceding decades of quality improvement methodologies such as quality control, TQM, and Zero Defects, based on the work of pioneers such as Shewhart, Deming, Juran, Ishikawa, Taguchi and others. In Engineering and Manufacturing, quality control and quality engineering are involved in developing systems to ensure products or services Total Quality Management ( TQM) is a business Management strategy aimed at embedding Awareness of Quality in all organizational processes " Zero Defects " is Step 7 of " Philip Crosby 's 14 Step Quality Improvement Process". Walter Andrew Shewhart (pronounced like "Shoe-heart" March 18, 1891 William Edwards Deming ( October 14, 1900 – December 20, 1993) was an American Statistician, Professor, Joseph Moses Juran ( December 24, 1904 – February 28, 2008) was a 20th century management consultant who is principally remembered as an Kaoru Ishikawa (石川馨 ( Ishikawa Kaoru) (1915-1989 was a Japanese University professor and influential quality management innovator best known in North America Gen'ichi Taguchi (田口 玄- Taguchi Genichi (born January 1, 1924 in Tokamachi, Japan) is an Engineer and Statistician

Like its predecessors, Six Sigma asserts that –

• Continuous efforts to achieve stable and predictable process results (i. e. reduce process variation) are of vital importance to business success. In Statistics, (statistical dispersion (also called statistical variability or variation) is variability or spread in a Variable or a Probability
• Manufacturing and business processes have characteristics that can be measured, analyzed, improved and controlled.
• Achieving sustained quality improvement requires commitment from the entire organization, particularly from top-level management.

Features that set Six Sigma apart from previous quality improvement initiatives include –

• A clear focus on achieving measurable and quantifiable financial returns from any Six Sigma project. [1]
• An increased emphasis on strong and passionate management leadership and support. [1]
• A special infrastructure of "Champions", "Master Black Belts", "Black Belts" etc. to lead and implement the Six Sigma approach. [1]
• A clear commitment to making decisions on the basis of verifiable data, rather than assumptions and guesswork. [1]

The term "Six Sigma" derives from a field of statistics known as process capability studies. A PROCESS is a unique combination of tools materials methods and people engaged in producing a measurable output for example a manufacturing line for machine parts Originally, it referred to the ability of manufacturing processes to produce a very high proportion of output within specification. Processes that operate with "six sigma quality" are assumed to produce defect levels below 3. 4 defects per million opportunities (DPMO). In Process improvement efforts defects per million opportunities or DPMO (or nonconformities per million opportunities ( NPMO) is a measure [4] 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. In some countries notably the United States, a Trademark used to identify a service rather than a product is called a service mark or servicemark Motorola Inc ( is an American, multinational Fortune 100, Telecommunications company based in Schaumburg Illinois. [5] Motorola has reported over US$17 billion in savings[6] from Six Sigma as of 2006. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Other early adopters of Six Sigma who achieved well-publicized success include Honeywell International (previously known as Allied Signal) and General Electric, where the method was introduced by Jack Welch. Honeywell ( is a major American multinational conglomerate company that produces a variety of consumer products engineering services and aerospace systems Italic text --> AlliedSignal was an aerospace automotive and engineering company that acquired and merged with Honeywell for$15 billion in 1999 John Francis "Jack" Welch Jr (born) was Chairman and CEO of General Electric between 1981 and 2001 [7] By the late 1990s, about two-thirds of the Fortune 500 organizations had begun Six Sigma initiatives with the aim of reducing costs and improving quality. Please do not add the complete list of fortune 500 companies The list is copyrighted by Fortune which makes money by selling the content [8]

In recent years, Six Sigma has sometimes been combined with lean manufacturing to yield a methodology named Lean Six Sigma. Lean manufacturing or lean production, which is often known simply as " Lean " is the practice of a theory of production that considers the expenditure

Graph of the normal distribution, which underlies the statistical assumptions of the Six Sigma model. The normal distribution, also called the Gaussian distribution, is an important family of Continuous probability distributions applicable in many fields The Greek letter σ marks the distance on the horizontal axis between the mean, µ, and the curve's point of inflection. In Mathematics and Statistics, the arithmetic Mean (or simply the mean) of a list of numbers is the sum of all the members of the list divided In Differential calculus, an inflection point, or point of inflection (or inflexion) is a point on a Curve at which the Curvature The greater this distance is, the greater is the spread of values encountered. For the curve shown in red above, µ = 0 and σ = 1. The other curves illustrate different values of µ and σ.

Origin and meaning of the term "six sigma process"

The following outlines the statistical background of the term Six Sigma.

Sigma (the lower-case Greek letter σ) is used to represent the standard deviation (a measure of variation) of a statistical population. Sigma (upper case Σ, lower case σ; Greek Σιγμα lower case in word-final position ς) is the eighteenth letter of the Greek In Probability and Statistics, the standard deviation is a measure of the dispersion of a collection of values In Statistics, a statistical population is a set of entities concerning which Statistical inferences are to be drawn often based on a Random sample 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. In Statistics, mean has two related meanings the Arithmetic mean (and is distinguished from the Geometric mean or Harmonic mean [9] This is based on the calculation method employed in a process capability study. A PROCESS is a unique combination of tools materials methods and people engaged in producing a measurable output for example a manufacturing line for machine parts

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, fewer standard deviations will fit between the mean and the nearest specification limit, decreasing the sigma number. [9]

Experience has shown that in the long term, processes usually do not perform as well as they do in the short. [9] 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. [9] To account for this real-life increase in process variation over time, an empirically-based 1. 5 sigma shift is introduced into the calculation. [10][9] 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 will move over time, or because the long-term standard deviation of the process will be greater than that observed in the short term, or both. [9]

Hence the widely accepted definition of a six sigma process is one that produces 3. 4 defective parts per million opportunities (DPMO). [11] This is based on the fact that a process that is normally distributed will have 3. The normal distribution, also called the Gaussian distribution, is an important family of Continuous probability distributions applicable in many fields 4 parts per million beyond a point that is 4. 5 standard deviations above or below the mean (one-sided capability study). [9] 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. [9] This is designed to prevent overestimation of real-life process capability. [9]

Methodology

Six Sigma has two key methodologies:[8] DMAIC and DMADV, both inspired by Deming's Plan-Do-Check-Act Cycle. William Edwards Deming ( October 14, 1900 – December 20, 1993) was an American Statistician, Professor, PDCA (" Plan-Do-Check-Act " is an iterative four-step problem-solving process typically used in Quality control. DMAIC is used to improve an existing business process; DMADV is used to create new product or process designs. [8]

DMAIC

The basic methodology consists of the following five steps:

• Define process improvement goals that are consistent with customer demands and the enterprise strategy.
• Measure key aspects of the current process and collect relevant data.
• Analyze the data to verify cause-and-effect relationships. Determine what the relationships are, and attempt to ensure that all factors have been considered.
• Improve or optimize the process based upon data analysis using techniques like Design of Experiments. Design of experiments, or experimental design, is the design of all information-gathering exercises where variation is present whether under the full control of the experimenter
• Control to ensure that any deviations from target are corrected before they result in defects. Set up pilot runs to establish process capability, move on to production, set up control mechanisms and continuously monitor the process. A PROCESS is a unique combination of tools materials methods and people engaged in producing a measurable output for example a manufacturing line for machine parts

The basic methodology consists of the following five steps:

• Define design goals that are consistent with customer demands and the enterprise strategy.
• Measure and identify CTQs (characteristics that are Critical To Quality), product capabilities, production process capability, and risks.
• Analyze to develop and design alternatives, create a 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 the production process and hand it over to the process owners.

DMADV is also known as DFSS, an abbreviation of "Design For Six Sigma". [8]

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. Statisticians work with theoretical and applied Statistics in both the private and public sectors 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. Martial arts are systems of codified practices and traditions of training for Combat.

Six Sigma identifies several key roles for its successful implementation. [12]

• Executive Leadership includes the CEO and other members of top management. 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 Six Sigma implementation across the organization in an integrated manner. The Executive Leadership draws them from upper management. Champions also act as mentors to Black Belts.
• Master Black Belts, identified by champions, act as in-house coaches on Six Sigma. They devote 100% of their time to Six Sigma. They assist champions and guide Black Belts and Green Belts. Apart from statistical tasks, their time is spent on ensuring consistent application of Six Sigma across various functions and departments.
• 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 objectives.
• 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. [13]

Quality management methods used in Six Sigma

Six Sigma makes use of a great number of established quality management methods that are also used outside of Six Sigma. The following table shows an overview of the main methods used.

 5 WhysAnalysis of varianceANOVA Gage R&RAxiomatic designBusiness process mappingCatapult exercise on variabilityCause & effects diagram (also known as fishbone or Ishikawa diagram)Chi-square test of independence and fitsControl chartCorrelationCost-benefit analysisCTQ treeCustomer surveyDesign of experiments Failure mode and effects analysisGeneral linear modelHistogramsHomogeneity of variancePareto chartPick chartProcess capabilityRegression analysisRun chartsSIPOC analysis (Suppliers, Inputs, Process, Outputs, Customers)StratificationTaguchi methodsThought process mapTRIZ

Criticism

Role of consultants

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 Toyota Production System (TPS combines management philosophy and practices to form an integrated socio-technical system at Toyota. For a topic outline on this subject see List of basic Japan topics. Six Sigma is often oversold by consulting firms that claim expertise in Six Sigma when they in fact only have a rudimentary understanding of the tools and techniques and the Six Sigma approach. [1]

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

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. Fortune is a Global Business Magazine published by Time Inc's Fortune|Money Group The S&P 500 is a Stock market index containing the stocks of 500 Large-Cap Corporations all of which are from the United States. " The statement is attributed to "an analysis by Charles Holland of consulting firm Qualpro (which espouses a competing quality-improvement process). "[15] 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. [16][17]

A Business Week article says that James McNerney's introduction of Six Sigma at 3M may have had the effect of stifling creativity. Walter James "Jim" McNerney Jr, is an American Businessman. 3M Company ( formerly Minnesota Mining and Manufacturing Company until 2002 is an American multinational conglomerate corporation with a worldwide It cites two Wharton School professors who say that Six Sigma leads to incremental innovation at the expense of blue-sky work. [18]

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. For other uses see Pacemaker (disambiguation A pacemaker (or artificial pacemaker, so as not to be confused with the heart's natural pacemaker Direct mail, also known as junk mail, advertising mail or admail, is the delivery of advertising material to recipients of postal Mail. The basis and justification for choosing 6 as the number of standard deviations is not clearly explained. [19] In addition, the Six Sigma model assumes that the process data always conform to the normal distribution. The normal distribution, also called the Gaussian distribution, is an important family of Continuous probability distributions applicable in many fields In reality, this assumption will often be mistaken, leading to a discrepancy between real and presumed defect rates. [1]

Because of its arbitrary nature, the 1. 5 sigma shift has been dismissed as "goofy" by the statistician Donald J. Wheeler. Donald J Wheeler is an internationally recognized expert on SPC and Data analysis. [20] Its universal applicability is seen as doubtful. [1]

Notes

1. ^ a b c d e f g h i j k Jiju Antony. Pros and cons of Six Sigma: an academic perspective. Retrieved on 1 May, 2008.
2. ^ Motorola University - What is Six Sigma?. Retrieved on 29 January, 2006.
3. ^ The Inventors of Six Sigma. Retrieved on 29 January, 2006.
4. ^ Motorola University Six Sigma Dictionary. Retrieved on 29 January, 2006.
5. ^ Motorola Inc. - Motorola University. Retrieved on 29 January, 2006.
6. ^ About Motorola University. Retrieved on 29 January, 2006.
7. ^ Six Sigma: Where is it now?. Retrieved on 22 May, 2008.
8. ^ a b c d Joseph A. De Feo & William 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
9. ^ a b c d e f g h i Tennant, Geoff (2001). SIX SIGMA: SPC and TQM in Manufacturing and Services. Gower Publishing, Ltd. , p. 25. ISBN 0566083744.
10. ^ Harry, Mikel (1988). The Nature of six sigma quality. Rolling Meadows, IL: Motorola University Press, p. 25. ISBN 9781569460092.
11. ^ Tonner, Craig; Patra, Pradeep (2003-09-03). Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Events 36 BC - In the Battle of Naulochus, Marcus Vipsanius Agrippa, Admiral of Octavian, defeats Sextus Pompeius Six Sigma (English). Retrieved on 2006-11-26. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 43 BC - The Second Triumvirate alliance of Gaius Julius Caesar Octavianus ("Octavian" later "Caesar Augustus"
12. ^ Mikel Harry & Richard Schroeder. Six Sigma, Random House, Inc, 2000. ISBN 0-385-49437-8
13. ^ iSixSigma Dctionary. Retrieved on 1 July, 2007.
14. ^ Scott Paton (2002-08). Juran: A Lifetime of Quality. Quality Digest. Retrieved on 2007-07-01. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. "July 1st" redirects here For the Ayumi Hamasaki song see H (song.
15. ^ Betsy Morris (2006-07-11). Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 911 - Signing of the Treaty of Saint-Clair-sur-Epte between Charles the Simple and Rollo of Normandy. Old rule: be lean and mean. Fortune. Retrieved on 2006-11-26. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 43 BC - The Second Triumvirate alliance of Gaius Julius Caesar Octavianus ("Octavian" later "Caesar Augustus"
16. ^ KAREN RICHARDSON (2007-01-07). Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1325 - Alfonso IV becomes King of Portugal. 1558 - France takes Calais, the last continental The 'Six Sigma' Factor for Home Depot. Wall Street Journal Online. Retrieved on 2007-10-15. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 533 - Byzantine General Belisarius makes his formal entry into Carthage, having conquered it from the
17. ^ Joe Ficalora & Joe Costello. Wall Street Journal SBTI Rebuttal. Sigma Breakthrough Technologies, Inc. . Retrieved on 2007-10-15. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 533 - Byzantine General Belisarius makes his formal entry into Carthage, having conquered it from the
18. ^ Hindo, Brian (6). At 3M, a struggle between efficiency and creativity. Business Week. Retrieved on 2007-06-06. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1508 - Maximilian I Holy Roman Emperor, is defeated in Friulia by Venetian forces; he is forced to sign a three-year
19. ^ Criticisms of Six Sigma - http://www.sixsigmaway.org/criticisms-of-six-sigma.html
20. ^ Wheeler, Donald J. , Phd, The Six Sigma Practitioner's Guide to Data Analysis, p. 307, http://www.spcpress.com

Literature

• Adams, Cary W. ; Gupta, Praveen; Wilson, Charles E. (2003). Six Sigma Deployment. Burlington, MA: Butterworth-Heinemann. ISBN 0750675233.