Six Sigma is a disciplined approach to business best practice that was designed to eliminate defects in production and uses data to drive its methodology. As can be imagined, its name is derived from statistics, or more precisely, the bell-curve representation of standard deviation. Six Sigma looks to the percentage of data points lying between two control values that form trigger boundaries. In this way, failures are measures as parts per million, representing the margin of error.
Six Sigma was originally brought into being by the Motorola Corp. The company deployed Six Sigma in the form of set practices designed to improve business processes by eliminating products or services that did not conform to design specifications. Since then many enterprises have adopted Six Sigma methods. These include GE, Merrill Lynch, Bank of America, Caterpillar, Honeywell and Raytheon.
Two popular Six Sigma methodologies are DMAIC (define, measure, analyze, improve, control) and DMADV (define, measure, analyze, design, verify) processes. Companies use DMAIC to improve existing process sets that are consistently falling below specification, and DMAIC is designed to garner incremental improvement. DMADV is used to develop new processes or products with high initial quality levels.
Any process in an organization can be implemented with Six Sigma. Although there are many examples of successful implementations of Six Sigma in organizations, the best of these are found in manufacturing, retail, sales and marketing. Those products or services that seek quality improvement are the type that mainly benefit from Six Sigma. Nevertheless, smaller deterministic steps are the easier way to achieving analysis, measurement and improvement.
A defect is defined in Six Sigma as being any product or service specification nonconformity. In essence, any process in Six Sigma cannot create more than 3.4 defects per million opportunities to be fully Six Sigma-compliant.
Much like other strategies for improvement in the workplace, Six Sigma processes are executed by individuals who have achieved a level of certification, benchmarked against a qualification scheme. In Six Sigma these are designated by colored belts (as in Karate.) The colors run from Six Sigma Green Belts at the bottom up to Master Black Belts at the top. Each level must be certified by the level above them.
Six Sigma activity dictates the use of Six Sigma tools often referred to as a "tool belt," and these are frequently found where Six Sigma is practiced. Some of the more common tools used in Six Sigma include thought process mapping, affinity diagrams, measurement system analysis, cause and effect analysis, mistake proofing and many others. A lot of these tools are like the ones used in the Toyota Production System (TPS) and enjoy the same Japanese nomenclature (e.g., Poka Yoke, mistake-proofing).