- management improvement methodology based on a heavy use of statistical tools to reduce errors and gain measurable cost savings. Six Sigma was developed at Motorola in the late 1980's. The name is taken from the measure of statistical variation (Sigma) with 6 Sigma representing fewer than 3.4 errors in every million opportunities for error.
In Six Sigma efforts a great deal of training is focused on the leaders of project teams. In companies, such as General Electric and Allied Signal, the requirements include four weeks of classroom training in advanced statistical methods, DMAIC process, design of experiments
, etc. which is spread out over four to twelve months allowing time for practical application of the learning on the job. Successful results from several projects to achieve "Black Belt" status is also a common requirement. "Black Belt" status can also be a requirement to move into senior management positions. Six Sigma does not require the amount of widespread training of most, or all employees, that characterized successful TQM efforts.
As with any widely adopted management methodology (such as "Total Quality Management") it has become difficult to define due to the wide variation among those organizations attempting to practice it. In the best applications, in my opinion, the focus of effort is not just defect prevention and cost avoidance but system improvement (for example, "design for Six Sigma") and customer satisfaction. Many Six Sigma efforts include a focus on lean thinking.
- 1.5 Sigma drift - the underpinning of Six Sigma equating to 3.4 errors per million opportunities is that a process will drift 1.5 around the mean. This contention is the subject of debate. Many statistician appose this belief, instead these statistician say, if the process is drifting it is not in statistical control. Which, then, calls into question the application of statistical tools that are only valid when the process is in statistical control.
- DMAIC process - Define, Measure, Analyze, Improve, and Control. The variation of the PDSA cycle used in the Six Sigma methodology.
- Black Belt - term used to describe Six Sigma practitioner of a certain level (what specifically it means varies depending on the organization and certification authority). In general, the highest level is "Master Black Belt", then "Black Belt", then "Green Belt" and some organizations also have "Yellow Belts." Normally the Mater Black Belt (in some cases the Black Belt) will report to a "Champion" or "Process Owner" or "Sponsor" on specific projects.
- Gauge R&R
- See Poka-Yoke description - it is next to impossible to reach 6 sigma type results without applying "Mistake-proofing" concepts.