Six Sigma is a methodology providing a way to detect errors before they occur in order to increase customer satisfaction. It is a statistical methodology providing companies with a way to make fewer mistakes in all their activities by eliminating discrepancies before they occur. Six Sigma is a highly disciplined systems approach that is based on working with data and facts. The general goal of Six Sigma is to master processes so that no more than 3.4 errors occur per million opportunities.
Sigma values are often expressed as "DPMO" (Defects Per Million Opportunities).