6 Sigma

A quality management system pioneered by Motorola and used by many manufacturing companies. Sigma refers to a standard deviation of a set of statistics. If defects occur according to a standard normal distribution, “six sigma” corresponds to approximately two quality failures per billion parts manufactured. In practical application of the Six Sigma methodology, however, the rate is taken to be 3.4 per million.
6 Sigma excels at improving manufacturing quality, particularly for critical products that can’t allow any defects (such as jet engines), but it hasn’t proven to be an effective approach for improving business processes, customer experiences, or internal corporate culture.
More information: www.6sigma.com