Lean Six Sigma Green Belt Exam Prep | 500+ Most
Tested QUESTIONs with Correct Answers & Expert
Rationales 2026/2027
QUESTION 1
Which DMAIC phase focuses on confirming the problem statement and
ensuring that the project scope is clearly defined with leadership
support?
• A. Measure
• B. Define
• C. Analyze
• D. Improve
Correct Answer: B. Define
Detailed Rationale: The Define phase is the foundational stage where
the team creates the Project Charter, defines the SIPOC, identifies
stakeholders, and secures buy-in from leadership.
QUESTION 2
What is the primary difference between a "Special Cause" and a
"Common Cause" variation?
• A. Common cause is predictable and inherent to the process;
special cause is unpredictable and external to the process.
• B. Special cause is predictable; common cause is random.
, • C. Common cause variations can be eliminated by standardizing
machines.
• D. There is no difference; all variation is bad.
Correct Answer: A. Common cause is predictable and inherent to the
process; special cause is unpredictable and external to the process.
Detailed Rationale: Common cause variation (noise) is always present.
Special cause variation (signal) arises from specific, identifiable
disruptions that need to be addressed.
QUESTION 3
Which of the following is considered "Waste" (Muda) according to the
Lean methodology?
• A. Time spent on value-added transformation.
• B. Waiting for approval or raw materials.
• C. Designing products according to customer specifications.
• D. Preventive maintenance on machines.
Correct Answer: B. Waiting for approval or raw materials.
Detailed Rationale: "Waiting" is one of the 8 Wastes of Lean
(TIMWOODS). It adds no value and consumes time in the process flow.
QUESTION 4
What is the statistical "Mode" of the following dataset: 5, 8, 8, 10, 12,
12, 12, 15?
• A. 10
• B. 12
, • C. 8
• D. 5
Correct Answer: B. 12
Detailed Rationale: The mode is the value that appears most frequently
in a dataset. 12 appears three times, more than any other number.
QUESTION 5
Which visual tool is used to display the frequency of defects and applies
the 80/20 rule to prioritize improvement efforts?
• A. Histogram
• B. Pareto Chart
• C. Control Chart
• D. Box Plot
Correct Answer: B. Pareto Chart
Detailed Rationale: A Pareto Chart highlights the "vital few" problems
(80% of issues) versus the "trivial many" (20% of issues), allowing teams
to focus on the highest impact areas.
QUESTION 6
If a process is normally distributed, what percentage of data falls within
±2 standard deviations from the mean?
• A. 68.27%
• B. 95.45%
• C. 99.73%
, • D. 99.99%
Correct Answer: B. 95.45%
Detailed Rationale: In a normal distribution, ±1𝜎 ≈ 68.27%, ±2𝜎 ≈
95.45%, and ±3𝜎 ≈ 99.73%.
QUESTION 7
What is the primary function of a "Value Stream Map" (VSM)?
• A. To calculate the exact cost of a product.
• B. To identify value-added and non-value-added steps in a process
flow to streamline it.
• C. To train new employees.
• D. To create a floor layout for a factory.
Correct Answer: B. To identify value-added and non-value-added steps
in a process flow to streamline it.
Detailed Rationale: VSM provides a holistic view of process and
material flow, allowing teams to visualize cycle times, wait times, and
waste.
QUESTION 8
Which of the following is the correct order of the DMAIC methodology?
• A. Define, Measure, Analyze, Improve, Control
• B. Design, Measure, Assess, Implement, Control
• C. Define, Monitor, Analyze, Improve, Check
• D. Develop, Measure, Assign, Implement, Conclude
Tested QUESTIONs with Correct Answers & Expert
Rationales 2026/2027
QUESTION 1
Which DMAIC phase focuses on confirming the problem statement and
ensuring that the project scope is clearly defined with leadership
support?
• A. Measure
• B. Define
• C. Analyze
• D. Improve
Correct Answer: B. Define
Detailed Rationale: The Define phase is the foundational stage where
the team creates the Project Charter, defines the SIPOC, identifies
stakeholders, and secures buy-in from leadership.
QUESTION 2
What is the primary difference between a "Special Cause" and a
"Common Cause" variation?
• A. Common cause is predictable and inherent to the process;
special cause is unpredictable and external to the process.
• B. Special cause is predictable; common cause is random.
, • C. Common cause variations can be eliminated by standardizing
machines.
• D. There is no difference; all variation is bad.
Correct Answer: A. Common cause is predictable and inherent to the
process; special cause is unpredictable and external to the process.
Detailed Rationale: Common cause variation (noise) is always present.
Special cause variation (signal) arises from specific, identifiable
disruptions that need to be addressed.
QUESTION 3
Which of the following is considered "Waste" (Muda) according to the
Lean methodology?
• A. Time spent on value-added transformation.
• B. Waiting for approval or raw materials.
• C. Designing products according to customer specifications.
• D. Preventive maintenance on machines.
Correct Answer: B. Waiting for approval or raw materials.
Detailed Rationale: "Waiting" is one of the 8 Wastes of Lean
(TIMWOODS). It adds no value and consumes time in the process flow.
QUESTION 4
What is the statistical "Mode" of the following dataset: 5, 8, 8, 10, 12,
12, 12, 15?
• A. 10
• B. 12
, • C. 8
• D. 5
Correct Answer: B. 12
Detailed Rationale: The mode is the value that appears most frequently
in a dataset. 12 appears three times, more than any other number.
QUESTION 5
Which visual tool is used to display the frequency of defects and applies
the 80/20 rule to prioritize improvement efforts?
• A. Histogram
• B. Pareto Chart
• C. Control Chart
• D. Box Plot
Correct Answer: B. Pareto Chart
Detailed Rationale: A Pareto Chart highlights the "vital few" problems
(80% of issues) versus the "trivial many" (20% of issues), allowing teams
to focus on the highest impact areas.
QUESTION 6
If a process is normally distributed, what percentage of data falls within
±2 standard deviations from the mean?
• A. 68.27%
• B. 95.45%
• C. 99.73%
, • D. 99.99%
Correct Answer: B. 95.45%
Detailed Rationale: In a normal distribution, ±1𝜎 ≈ 68.27%, ±2𝜎 ≈
95.45%, and ±3𝜎 ≈ 99.73%.
QUESTION 7
What is the primary function of a "Value Stream Map" (VSM)?
• A. To calculate the exact cost of a product.
• B. To identify value-added and non-value-added steps in a process
flow to streamline it.
• C. To train new employees.
• D. To create a floor layout for a factory.
Correct Answer: B. To identify value-added and non-value-added steps
in a process flow to streamline it.
Detailed Rationale: VSM provides a holistic view of process and
material flow, allowing teams to visualize cycle times, wait times, and
waste.
QUESTION 8
Which of the following is the correct order of the DMAIC methodology?
• A. Define, Measure, Analyze, Improve, Control
• B. Design, Measure, Assess, Implement, Control
• C. Define, Monitor, Analyze, Improve, Check
• D. Develop, Measure, Assign, Implement, Conclude
