The term Six Sigma originated from terminology associated with manufacturing, specifically terms associated with statistical modeling of manufacturing processes. The maturity of a manufacturing process can be described by a sigma rating indicating its yield, or the percentage of defect-free products it creates. A six sigma process is one in which 99.99966% of the products manufactured are statistically expected to be free of defects (3.4 defects per million) [DPMO : Defects Per Million Opportunities]. Motorola set a goal of "six sigma" for all of its manufacturing operations, and this goal became a byword for the management and engineering practices used to achieve it.
Six Sigma measures defects in million ‘opportunities’ and assigns ‘levels’. There are six such levels. An organizations is said to be at 6 sigma level if it has 3.4 defects per million opportunities. This is the highest level an organization can attain. Average American company is at 4 sigma level. That is equivalent to 6,210 defects per million opportunities.
Six Sigma seeks to improve the quality of process outputs by identifying and removing the causes of defects (errors) and minimizing variability in manufacturing and business processes. It uses a set of quality management methods, including statistical methods, and creates a special infrastructure of people within the organization ("Black Belts", "Green Belts", etc.) who are experts in these methods. 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).
Six Sigma measures defects in million ‘opportunities’ and assigns ‘levels’. There are six such levels. An organizations is said to be at 6 sigma level if it has 3.4 defects per million opportunities. This is the highest level an organization can attain. Average American company is at 4 sigma level. That is equivalent to 6,210 defects per million opportunities.
Six Sigma seeks to improve the quality of process outputs by identifying and removing the causes of defects (errors) and minimizing variability in manufacturing and business processes. It uses a set of quality management methods, including statistical methods, and creates a special infrastructure of people within the organization ("Black Belts", "Green Belts", etc.) who are experts in these methods. 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).
| Sigma level | DPMO | Percent defective | Percentage yield | Short-term Cpk | Long-term Cpk |
|---|---|---|---|---|---|
| 1 | 691,462 | 69% | 31% | 0.33 | –0.17 |
| 2 | 308,538 | 31% | 69% | 0.67 | 0.17 |
| 3 | 66,807 | 6.7% | 93.3% | 1.00 | 0.5 |
| 4 | 6,210 | 0.62% | 99.38% | 1.33 | 0.83 |
| 5 | 233 | 0.023% | 99.977% | 1.67 | 1.17 |
| 6 | 3.4 | 0.00034% | 99.99966% | 2.00 | 1.5 |
| 7 | 0.019 | 0.0000019% | 99.9999981% | 2.33 | 1.83 |
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