Six Sigma is a methodology
Six Sigma is a methodology to manage process variations that cause defects, defined as unacceptable deviation from the mean or target; and to systematically work towards managing variation to eliminate those defects.
The objective of Six Sigma is to deliver high performance, reliability, and value to the end customer. It was pioneered by Bill Smith at Motorola in 1986 and was originally defined as a metric for measuring defects and improving quality; and a methodology to reduce defect levels below 3.4 Defects Per (one) Million Opportunities (DPMO). Six Sigma has now grown beyond defect control.
Six Sigma is a registered service mark and trademark of Motorola, Inc. Motorola has reported over US$17 billion in savings from Six Sigma to date.