The central idea behind Six Sigma is that if the number of "defects" in a process can be measured, it is possible to systematically figure out how to eliminate them to get as close to "zero defects" as possible.
The term sigma, in the name Six Sigma, is a Greek letter used to describe variability, in which a classical measurement unit consideration of the initiative is defects per unit. Sigma quality level offers an indicator of how often defects are likely to occur: a higher sigma quality level indicates a process that is less likely to create defects.
During a period of over ten years from the mid-1980s, a consortium inclduing Motorola developed its own quality approach, based on the best elements taken from existing quality ideas dating back to the 1950s, and from current Japanese practices. Ultimately called Six Sigma, this concept of a quality metric was peculiar to Motorola for many years, although the American motor car manufacturing industry had for some time used four-and-a-half sigma as the standard.
To achieve Six Sigma, a process must not produce more than 3.4 defects per million opportunities. A Six Sigma defect is defined as anything outside of customer specifications. A Six Sigma opportunity is then the total quantity of chances for a defect.
Six Sigma is a disciplined and quantitative approach involving setting up a system and process for the improvement of defined metrics in manufacturing, service, or financial processes. The approach drives the overall process of selecting the right projects based on an organization's business goals and selecting and training the right people to obtain the results. Improvement projects follow a disciplined process defined by a system of four macro phases: measure, analyze, improve, control (MAIC).
Six Sigma quality methodology uses the very best from existing Total Quality Management together with Statistical Process Control and Measurement, and strong Customer Focus, and therefore impacts on three key areas: the process, the employee, and the customer. Successful implementation requires Strategy Management and Cultural Change across the entire company.
Surveys show that about 25 percent of respondents have been implementing Six Sigma. The number of companies implementing Six Sigma has grown by an order of magnitude. The number of companies implementing Six Sigma is split between manufacturing and nonmanufacturing companies. The companies implementing Six Sigma are quite uniformly distributed by company size.
In recent years, companies as varied as DuPont (DD ), Textron (TXT ), Bank of America (BAC ), and Sun Microsystems (SUNW ) have all made Six Sigma bedrocks of their culture. Hybrid formulas have spawned, such as Lean Six Sigma and Design for Six Sigma.
Six Sigma teams use a methodology called DMAIC, which is an acronym for “determine, measure, analyze, implement and control.” The team works in isolation to develop, apply and test any solution. Lean Six Sigma rejects the “front-loading” method of decision-making in favor of making decisions based on observation. Workers engage in “knowledge creation” through short learning cycles, which reveal problems and solutions through observation.
The most crucial phase of Sigma methodology is the statistical measurement and analysis that is concerned with assessing the degree of achieved results and comparing this with the expected results. The data will then be harnessed and taken through various statistical tests in order to come up with a solution that will counter the cause of the differences that arise in the product or service.
Within the Six Sigma methodology there are various "Six Sigma Belts" and other key roles that have specific responsibilities.
Each Six Sigma belt represents a different level of expertise in the field of Six Sigma.