Six Sigma is a statistical methodology for improving quality and reducing defects. It aims for near perfect accuracy, with the goal of fewer than 3.4 defects per million opportunities. Six Sigma was introduced by Motorola in 1987 and uses a define-measure-analyze-improve-control methodology. It has been adopted by many companies and led to billions of dollars in savings at places like GE and Motorola through eliminating defects and improving processes.