Six sigma is a quality management program that measures and improves the operational performance of a company by identifying and correcting the defects in the company's processes and products. Originally, six sigma was defined as a process variation that would produce no more than 3.4 defects per million parts (or "opportunities.") Today, however, six sigma is applied to produce a product that satisfies the customer and minimizes supplier losses to the point at which it is not cost effective to pursue a higher quality.
Six Sigma was pioneered at Motorola in the mid 1980s by Bob Galvin, who succeeded his father, Paul Galvin, as head of the company, and by Motorola engineer Bill Smith. While Motorola still maintains the trademark, the methods associated with the term were picked up and followed by other large companies such as AlliedSignal (now known as Honeywell) and General Electric, which ultimately popularized the process. It has since spread to other large companies, including Ford, Caterpillar, Microsoft, Raytheon, Quest Diagnostics, Seagate Technology, Siemens and many more.