Six Sigma (6σ) is a management methodology developed by Motorola in the USA in 1987. It is focused on improvement of the quality of business processes by determining the causes of defects or failures, through which the variance in the processes can be reduced or eliminated. It exists of a set of quality management methods, including statistical methods en is organizational secured by special functions with special expertise, like Black Belts, Green Belts en Yellow Belts. A Six Sigma project follows a pre- determined number of steps and has quantified objectives.

Six Sigma originates from statics and is strongly focused on data gathering in order to reduce variation. Within statistics sigma stands for variation around the mean. The maturity of a process can be describes according to a sigma rating. A Six Sigma quality performance means no more than 3.4 defects per million opportunities.

Motorola had a target of six sigma for their production processes, consequently the term was used for all management and technical activities in order to achieve this goal. Six Sigma became well known after broad application by General Electric in 1995 (estimated savings of $ 11 billion within 5 years).