Six Sigma is a disciplined, data-driven approach and methodology for eliminating defects in any process. In order to achieve Six Sigma a process must not produce more than 3.4 defects per million opportunities.
The methodology was first introduced by engineer bill Smith whilst working at Motorola and became popularised after Jack Welch made it central to business strategy at General Electric in 1995. The fundamental objective of the Six Sigma is the implementation of a measurement-based strategy that focuses on process improvement and variation reduction.
Within Six Sigma there are two key frameworks, DMAIC which focuses on improving business processes and DMADV which focuses on the creation of new processes, products and services.