Green Belt Exam Cheat Sheet: DMAIC, Key Formulas, and the Tools for Each Phase
A one-page review for Six Sigma Green Belt candidates, whichever certifying body you’re testing with.
Before you start: Several organizations offer Six Sigma Green Belt certification, and their exams differ in length, format, and whether reference materials are allowed. This green belt exam cheat sheet covers the core body of knowledge they share. Check your certifying body’s rules for exactly what you can bring.
Green Belt exams test whether you can apply DMAIC and basic statistics to real problems. This green belt exam cheat sheet condenses the phases, tools, and formulas you’ll use most.
Green Belt Exam Cheat Sheet: DMAIC Phases and Tools
| Phase | Goal | Common tools |
|---|---|---|
| Define | Clarify the problem, scope, and customer needs | Project charter, SIPOC, voice of the customer, CTQ tree |
| Measure | Establish the baseline | Data collection plan, process map, measurement system analysis (gage R&R), process capability |
| Analyze | Find root causes | Fishbone diagram, 5 Whys, Pareto chart, hypothesis tests, regression |
| Improve | Develop and test solutions | Brainstorming, design of experiments, pilot testing, FMEA |
| Control | Sustain the gains | Control charts, control plan, standard work, mistake-proofing (poka-yoke) |
Key Formulas
- DPMO: (Defects ÷ (Units × Opportunities per unit)) × 1,000,000.
- Six Sigma benchmark: 3.4 DPMO (with the conventional 1.5-sigma shift).
- Cp (potential capability): (USL − LSL) ÷ 6σ.
- Cpk (actual capability): The smaller of (USL − μ) ÷ 3σ and (μ − LSL) ÷ 3σ.
- Rolled throughput yield (RTY): Multiply the first-pass yields of each step.
Statistics Essentials
Center and Spread
Mean, median, and mode describe center. Range, variance, and standard deviation describe spread.
Normal Distribution
About 68% of data falls within ±1σ, 95% within ±2σ, and 99.7% within ±3σ of the mean.
Hypothesis Testing
H₀ = no difference. If the p-value is below α (often 0.05), reject H₀. Type I error = false positive; Type II error = false negative.
Control Charts
Common cause variation is natural; special cause variation signals something changed. Points outside control limits or unusual patterns call for investigation.
Lean Wastes
Remember TIMWOODS:
- Transportation: Unnecessary movement of materials.
- Inventory: Excess stock.
- Motion: Unnecessary movement of people.
- Waiting: Idle time.
- Overproduction: Making more than needed.
- Overprocessing: More work than the customer values.
- Defects: Errors and rework.
- Skills: Unused talent and ideas.
Key Takeaways
- Know the goal and main tools of each DMAIC phase.
- Memorize DPMO, Cp, Cpk, and RTY.
- Understand the 68–95–99.7 rule and how to read a p-value.
- Tell common cause from special cause variation on control charts.
- Use TIMWOODS for the eight lean wastes.
Frequently Asked Questions
What does DMAIC stand for?
DMAIC stands for Define, Measure, Analyze, Improve, and Control — the five-phase improvement method used in Six Sigma projects.
What is the difference between Cp and Cpk?
Cp measures potential capability based on spread alone, while Cpk also accounts for how well the process is centered between the specification limits.
Can I bring notes into a Green Belt exam?
It depends on the certifying body. Some allow reference materials and others don’t, so check your exam’s rules before test day.
What is DPMO in Six Sigma?
DPMO means defects per million opportunities. It’s calculated by dividing defects by total opportunities and multiplying by one million.
The Bottom Line
This green belt exam cheat sheet captures the structure and math behind Six Sigma. Learn DMAIC inside out, practice the formulas, and you’ll be ready for both the exam and real projects.
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