Which quality improvement methodology uses statistics to measure variation in a process with the aim of producing error-free results?

• A. Lean
• B. Process redesign
• C. QI toolbox techniques
• D. Six Sigma

Answer: (D)

Six Sigma centers on using statistics to understand and minimize variation in a process, with the goal of producing near-zero defects. It relies on data-driven analysis to identify why a process deviates from customer requirements and to confirm that improvements actually reduce variation. Tools like control charts and process capability indices (Cp, Cpk) quantify how a process behaves and how well it fits within specification, often expressed in defects per million opportunities. The approach typically follows a structured DMAIC cycle—define, measure, analyze, improve, and control—to ensure changes stick and performance is sustained. While Lean emphasizes eliminating waste and speeding flow, and broad QI toolbox techniques cover various methods, Six Sigma uniquely centers on statistical measurement of variation to drive defect reduction.