Which set of concepts focuses on reducing variability in processes and defects in products, often cited as a standard with 3.4 defects per million opportunities?

• A. Lean manufacturing
• B. Total Quality Management
• C. Continuous improvement
• D. Six Sigma quality

Answer: (D)

Six Sigma quality centers on reducing variability in processes and the number of defects in products. It aims for very near-perfect performance, often quantified as 3.4 defects per million opportunities—the six-sigma level. This target comes from a data-driven approach that uses DMAIC for improving existing processes, along with statistical tools to understand and control variation.

Lean focuses on eliminating waste and improving flow, not on a specific defect-rate target. Total Quality Management is a broad organizational quality philosophy rather than a defined metric. Continuous improvement is a general mindset of ongoing enhancements without prescribing a fixed defect-rate standard.