6 sigma methodology was introduced in 1986 by Motorola company, to resolve quality related problems. 6 sigma gained popularity among manufacturers in 1995 after Jack Welch made it principal business strategy at General Electric.
The name of methodology arises from greek letter σ (sigma). In statistics it means a standard deviation from the mean. Achieving sixth sigma level is equivalent to perfect quality.
* DPMO – Defects per million opportunities