Lean Six Sigma training
RecommendedIASSC recommends training from a qualified institution, Lean Six Sigma trainer or corporate program.
IASSC Certified Lean Six Sigma Green Belt (ICGB) Exam Guide
Validates knowledge of Lean Six Sigma problem solving, covering DMAIC phases, lean tools and statistical analysis.
The exam checks that you can choose and apply the right tool at each DMAIC phase, with a heavy share of statistics, including non-parametric tests. It is closed book, so you need to know which test or chart fits a situation without looking anything up.
Understand the exam
Syllabus
IASSC draws about 20 questions from each of the five phases (100 scored in total).
1.0Define phaseAbout 20 questions
- 1.1The basics of Six Sigma
- 1.2The fundamentals of Six Sigma
- 1.3Selecting Lean Six Sigma projects
- 1.4The lean enterprise
Example scenario: A process has 250 defects across 1,000 units with 5 opportunities per unit. How would you express its performance as DPMO, and why is that better than a defect percentage for comparing processes?
2.0Measure phaseAbout 20 questions
- 2.1Process definition
- 2.2Six Sigma statistics
- 2.3Measurement system analysis
- 2.4Process capability
Example scenario: A gauge study shows that most of the variation in readings comes from different operators measuring the same part. Which part of the measurement system is the problem, and what would you do first?
3.0Analyze phaseAbout 20 questions
- 3.1Patterns of variation
- 3.2Inferential statistics
- 3.3Hypothesis testing
- 3.4Hypothesis testing with normal data
- 3.5Hypothesis testing with non-normal data
Example scenario: Two shifts’ cycle times are clearly skewed, and the samples are small. Which family of tests would you choose to compare their medians, and why not a t-test?
4.0Improve phaseAbout 20 questions
- 4.1Simple linear regression
- 4.2Multiple regression analysis
Example scenario: A regression of cycle time on batch size has a strong R-squared, but the residuals fan out as batch size grows. What does that tell you about using the model for prediction?
5.0Control phaseAbout 20 questions
- 5.1Lean controls
- 5.2Statistical process control (SPC)
- 5.3Six Sigma control plans
Example scenario: You want to detect a small, sustained shift in a process mean quickly. Which control chart suits that better than a standard Xbar chart, and what is its trade-off?
Official IASSC Green Belt Body of Knowledge · BoK v3.2
Format
- Questions
- 100
- Duration
- 3h
- Passing score
- 70%
- Delivery
- Test centre or online
- Languages
- English, French, Japanese, Spanish
Question types
Read a short scenario or data summary and choose the one correct answer from the options.
CertUp example
Cycle times from two shifts are clearly skewed and the samples are small. Which test compares them without assuming normal data?
Show answer
Mann-Whitney test. It compares two groups without assuming the data are normal, which suits skewed data and small samples.
Read a statement and decide whether it is true or false.
CertUp example
True or false: a process can be stable on a control chart and still fail to meet customer specifications.
Show answer
True. Control limits describe what the process does, while specifications describe what the customer needs; the two are separate.
Eligibility and booking
Buy an on-demand voucher, then schedule your exam. For the online route, an IASSC proctor meets you in a virtual testing room, checks your ID by webcam and stays with you through the exam. IASSC also lists test centres and accredited providers.
Make a study plan
Read the Body of Knowledge and try the Evaluation Exam first, so you can see which phases are weakest. Spend most of your time on the sections where you score lowest, which is often the statistics.
Most candidates spend 40–90 hours. Plan for the low end if you already use these tools at work; add time if hypothesis testing or regression are unfamiliar.
- 1Understand the examRead the syllabus and format, check you’re eligible and pick a target date.4 h
- 3Learn the core conceptsWork through one main course or book, topic by topic.48 h
- 4Practice with mock examsTake timed practice tests and review every mistake.24 h
- 5Prepare for exam dayBook the exam and check the ID and delivery rules.4 h
Learn the core concepts
There is no IASSC textbook, so use the free Body of Knowledge as your syllabus and pick one main course that follows it.
Best video courseCertified Lean Six Sigma Green Belt Training (Accredited)
Best live instructionLean Six Sigma Green Belt Certification Training
Best official syllabusIASSC Green Belt Body of KnowledgeAdd the non-parametric tests. ASQ-based books give them little space, so learn Mann-Whitney, Kruskal-Wallis, Mood’s median and Friedman from your course or another source.
Practice with mock exams
IASSC’s own Evaluation Exam is the closest practice. Use it to find weak phases, then retake it after studying.
Free Lean Six Sigma Green Belt Practice Test
IASSC Green Belt Evaluation ExamIASSC ICGB Lean Six Sigma Green Belt exam prep 2026Are you ready?
- You can choose the right hypothesis test, normal or non-normal, for a scenario.
- You can calculate DPMO, RTY and capability indices without a formula sheet.
- You can explain why each wrong option in a practice question is wrong.
- You score consistently above the 70% pass mark on Evaluation Exam retakes.
Prepare for exam day
The exam is closed book. Follow the checklist for your delivery route.
Before testing with online proctoring
Before testing at a centre or accredited provider
- Run the compatibility check at least 24 hours ahead on the same computer, network and room, and again about two hours before the exam.
- Show the same valid, original, government-issued photo ID you used to book; a name mismatch means no test and no refund.
- Use a private room with one visible doorway and a clear desk, and be ready for a 360-degree camera scan.
- Close chat, screen-sharing and virtual machine software, and turn off browser extensions, including AI and translation tools.
- Use a computer with a working webcam; a phone cannot replace it.
- Book the centre or accredited provider that delivers IASSC exams in your area.
- Bring the same photo ID you used when booking, matching your name exactly.
- Bring no notes or reference material; the exam is closed book.
Advice from exam takers
Retake the Evaluation Exam and review every miss.
One passer retook IASSC’s Evaluation Exam five times in the 20-day window, noting why each missed question was wrong, and says each retake included some different questions. They found the official exam harder than the Evaluation Exam.
Learn the non-parametric tests.
A passer who studied from the ASQ handbook says it barely covers Mann-Whitney, Kruskal-Wallis, Mood’s median and Friedman, and thinks these were a large part of the exam. Another passer says no single course covered the whole IASSC outline.
Expect concepts, a little history and little calculation.
Passers say the exam asks which tool to use and why rather than formula recall. Two questions covered the history of Six Sigma, and one passer lists Z values and the regression coefficient as the main calculations.