Overview

Six Sigma Overview & DMAIC

What Six Sigma is, the belt hierarchy, and the DMAIC improvement roadmap.

~7 min read·3 sections·4 key terms

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What Six Sigma Is

Six Sigma is a data-driven methodology for reducing DEFECTS and VARIATION in a process. The name comes from the goal of fitting six standard deviations between the process mean and the nearest specification limit — equating to about 3.4 defects per million opportunities (DPMO).

The core idea: reduce variation, and quality and predictability improve.

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The Belt Hierarchy

• WHITE/YELLOW BELT — basic awareness, supports projects. • GREEN BELT — leads smaller projects, assists Black Belts, works part-time on Six Sigma. • BLACK BELT — leads complex projects full-time, mentors Green Belts. • MASTER BLACK BELT — trains and coaches Black Belts, manages the program. • CHAMPION/SPONSOR — executive who removes barriers and selects projects.

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DMAIC

DMAIC is the improvement roadmap for existing processes: • DEFINE — the problem, goal, scope, and customer (CTQ). • MEASURE — collect baseline data, validate the measurement system. • ANALYZE — find root causes of variation/defects. • IMPROVE — develop and implement solutions. • CONTROL — sustain the gains with monitoring.

For designing new processes, DMADV (Define, Measure, Analyze, Design, Verify) is used instead.

📖 Key Terms

DPMO: Defects Per Million Opportunities; Six Sigma targets about 3.4.
Variation: The fluctuation in a process output that Six Sigma seeks to reduce.
DMAIC: Define, Measure, Analyze, Improve, Control — the improvement roadmap.
Black Belt: A full-time leader of complex Six Sigma projects who mentors Green Belts.

💡 Exam Tips

▸Six Sigma ≈ 3.4 defects per million opportunities (DPMO).
▸DMAIC = Define, Measure, Analyze, Improve, Control.
▸DMADV is for designing NEW processes; DMAIC improves EXISTING ones.
▸Black Belts lead full-time; Green Belts lead smaller projects part-time.