Overview: Six Sigma and the Organization
Three faces of Six Sigma
Six Sigma is a metric (3.4 defects per million opportunities, assuming a 1.5-sigma long-term shift, i.e. 99.99966% yield), a methodology (DMAIC for improving existing processes, DFSS/DMADV for designing new ones), and a management system (roles, project selection tied to strategy, tollgate governance).
Roles
An executive sponsor or champion funds the project and removes barriers. The Master Black Belt is the technical coach and deployment leader. Black Belts lead cross-functional projects full time; Green Belts lead projects part time inside their own work area. The process owner inherits and sustains the improvement after the team disbands. Questions about who keeps the gain alive after closure are pointing at the process owner, not the Belt.
Lean, variation, and cost of poor quality
Lean removes waste and shortens lead time; Six Sigma reduces variation and defects. They are complementary, not competing. Cost of poor quality (COPQ) includes internal failure, external failure, appraisal, and prevention costs. Typical organizations lose 15-25% of revenue to poor quality; world-class performers lose about 1%.
Traps
Sigma level and DPMO conversions that ignore the 1.5-sigma shift; classifying inspection as prevention; treating an IT installation as an improvement when no metric moves; and confusing a champion with a process owner.
Worked example
A process runs at 6,210 DPMO. On the standard short-term table that is a 4-sigma process. At 233 DPMO it would be 5 sigma; at 66,807 DPMO, 3 sigma. Rule of thumb: each sigma level gained cuts defects by roughly an order of magnitude.