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Six Sigma was pioneered by Bill Smith at Motorola in 19861. Originally, it was defined2 as a metric for measuring defects and improving quality; and a methodology to reduce defect levels below 3.4 Defects Per (one) Million Opportunities (DPMO). Six Sigma is a registered service mark and trademark of Motorola, Inc 3. Motorola has reported over US$17 billion savings4 from Six Sigma to date. AlliedSignal and GE became early adopters of Six Sigma and reported benefits of over US$300 million during its first year of application5. Their CEOs, Larry Bossidy and Jack Welch, played a vital role in popularizing Six Sigma. Other major organizations who claim to have benefited from Six Sigma implementation are Ford , Caterpillar , Microsoft , Raytheon , Quest Diagnostics , Seagate Technology , Siemens , Merrill Lynch , Lear , 3M and many more. DEFINITION Six Sigma has now grown beyond defect control. It can be defined 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 defects6. The objective of Six Sigma is to deliver world-class performance, reliability, and value to the end customer. APPLICATION & SUCCESS Starting with Manufacturing , today Six Sigma is being widely used across a wide range of industries like banking, business process outsourcing (BPO), telecommunications, insurance, construction, healthcare7, and software8. Some non-manufacturing examples are given below: Healthcare North Carolina Baptist Hospital says9, "The Six Sigma process improvement deployment at North Carolina Baptist Hospital is starting to show the kind of results that convert skeptics to believers." and "A Six Sigma process improvement team charged with getting heart attack patients from the Emergency Department into the cardiac catheterization lab for treatment faster slashed 41 minutes off the hospital's mean time" Banking Bank of America has used Six Sigma for credit risk assessment reduction, fraud prevention, and customer satisfaction improvement, etc. Bank of Americas Six Sigma initiative resulted in benefits of more than US$2 billion; and increased customer satisfaction by 25%10. Insurance Insurance companies have used Six Sigma for various critical tasks like premium outstanding reduction and various cycle time reductions. For example, CIGNA Dental reports pending claim volume reduction by over 50% 11. Construction In Engineering and Construction, on the Channel Tunnel Rail Link project in the UK, the Bechtel’s project team12 uncovered a way to save hundreds of job hours on one of the tunneling jobs. The Institute of Quality Assurance has interesting success stories13 on Wipro , Citibank , and Motorola. Military The United States Navy has adopted Six Sigma as part of AIRSpeed, an overall set of practices designed to improve efficiency in aviation maintenance. The other components are Lean Manufacturing , '' Kaizen '', and Theory Of Constraints . METHODOLOGY Six Sigma has two key methodologiesJoseph 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 – DMAIC and DMADV. DMAIC is used to improve an existing business process. DMADV is used to create new product designs or process designs in such a way that it results in a more predictable, mature and defect free performance. Sometimes a DMAIC project may turn into a DFSS project because the process in question requires complete re-design to bring about the desired degree of improvement. DMAIC Basic methodology consists of the following five phases:
DMADV Basic methodology consists of the following five phases:
Also see Design For Six Sigma quality. ROLES REQUIRED FOR IMPLEMENTATION Six Sigma identifies five key rolesMikel Harry & Richard Schroeder. ''Six Sigma'', Random House, Inc, 2000. ISBN 0-385-49437-8 for its successful implementation.
Specific training programs are available to train people to take up these roles. The above listed roles conform to the old Mikel Harry / Richard Schroeder model, which is far from being universally accepted. In many successful programs, both Green Belts and Black Belts lead projects, and work on problems in their existing area of responsibility. EXAMPLES OF SOME KEY TOOLS USED
CRITICISMS OF SIX SIGMA Of its origin Some argue that Robert Galvin and Bill Smith did not really "invent" Six Sigma in the 1980s, but rather applied methodologies that had been available since the 1920s and were developed by luminaries like Shewhart , Deming , Juran , Ishikawa , Ohno , Shingo , Taguchi and Shainin {Link without Title} . 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. The use of "Black Belts" as itinerant change agents is controversial as it has created a cottage industry of training and certification which arguably 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. Of the term: Six Sigma " Sigma " (the lower case Greek letter) is used to represent Standard Deviation , a measure of variation. The term "six sigma" comes from the notion that if you have six standard deviations between the Mean of a process and the nearest specification limit, you will make practically no items that exceed the specifications. This is the basis for the Process Capability study, often used by quality professionals, and the term “six sigma” has its roots in this tool. Criticism of the tool itself, and the way that the term was derived from the tool often sparks criticism of six sigma. It is often said that a six sigma process produces 3.4 defective parts per million. A process that is Normally Distributed will have 3.4 parts per million beyond a point that is 4.5 standard deviations above the mean. A Capability Study on normally distributed data, mean 0, standard deviation 1, with an upper specification limit of 4.5 will confirm this. Some six sigma practitioners call this 4.5 sigma process a 6 sigma process by invoking the 1.5 sigma shift. This is a notion that has existed since before Motorola’s program, and which gets little acceptance from professional statisticians. Donald Wheeler, one of the most respected workers in statistics, dismisses it as "goofy". As sample size increases, the error in the estimate of standard deviation converges much more slowly than the estimate of the mean (see Confidence Interval ). Even with a few dozen samples, the estimate of standard deviation often drags an alarming amount of uncertainty into the Capability Study calculations. It follows that estimates of defect rates can be very greatly influenced by uncertainty in the estimate of standard deviation. Estimates for the number of defective parts per million produced depend on knowing something about the shape of the distribution from which the samples are drawn. Unfortunately, we have no means for proving that data belong to any particular distribution. We only assume normality, based on finding no evidence to the contrary. Estimating defective parts per million down into the 100’s or 10’s of units based on such an assumption is wishful thinking, since actual defects are often deviations from normality, which have been assumed not to exist. In summary, the term “six sigma” has its roots in a quality tool that can easily be misapplied by a naïve user and to the controversial 1.5 sigma shift. Of statistics 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 . The 1.5 sigma shift theory is often criticized by statisticans that the sample size is too small to make mathematically justified predictions. In addition, there are some "annoying" things, such as clinging to the outdated model of "attribute" and "variable" data, rather than the much more widely accepted "nominal", "ordinal", "interval", and "ratio" model. There is also the problem that the widely used Capability Study drags an alarmingly high level of uncertainty into its calculations, and is often given credit for more than it can usually do. Of methods Others suggest that Six Sigma, rather than being a true methodology, is more often implemented to start an unending cycle of improvement and use of better tools on the industry day-to-day practices rather than to use advanced statistical theories that cannot be daily applied. Of effects There has been some controversy over the level of Six Sigma's effects, with some believing that its benefits have been vastly overstated. In addition, in companies not solely devoted to manufacturing (with GE, the owner of NBC & Universal Studios, being the prime example), the spillover effects of Six Sigma have been troubling. Executives trained in the ways of Six Sigma often clash with the "creative types" who must be a part of such companies. REFERENCES SEE ALSO
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