Six Sigma Green Belt
Certification Exam Review
100 Practice Questions with Correct Answers and Rationales
2026/2027 Edition
ASQ / IASSC / CSSC Professional Certification Preparation
, Six Sigma Green Belt Certification Exam Review | 2026/2027
Domain 1: Overview and Fundamentals (Questions 1–12)
Question 1
The primary objective of Six Sigma methodology is to:
A) Maximize production output at any cost
B) Reduce process variation and eliminate defects to achieve consistent quality
C) Increase the number of quality inspection checkpoints
D) Replace all manual processes with automated systems
Correct Answer: B) Reduce process variation and eliminate defects to achieve consistent
quality
Rationale: Six Sigma aims to reduce process variation and eliminate defects, targeting no
more than 3.4 defects per million opportunities (DPMO). The focus is on data-driven process
improvement rather than inspection-based quality or mere output maximization. Increasing
inspections is contrary to Six Sigma philosophy, which emphasizes prevention over detection.
Question 2
Which of the following best describes the role of a Six Sigma Green Belt within an organization?
A) A full-time quality improvement leader who mentors Black Belts
B) A part-time project leader who leads improvement projects while maintaining other job
responsibilities
C) An executive sponsor who allocates resources for Six Sigma initiatives
D) A statistical consultant who only performs data analysis
Correct Answer: B) A part-time project leader who leads improvement projects while
maintaining other job responsibilities
Rationale: The Green Belt typically leads improvement projects part-time while maintaining
their regular role. They apply DMAIC methodology, collect and analyze data, and implement
solutions within their functional area. Master Black Belts mentor Black Belts, Champions are
executive sponsors, and Green Belts are not limited to statistical analysis only.
Question 3
In the context of Lean principles, which of the following represents the seven wastes
(TIMWOOD)?
A) Time, Inventory, Motion, Waiting, Overproduction, Over-processing, Defects
B) Training, Information, Materials, Workforce, Organization, Output, Delivery
C) Technology, Integration, Maintenance, Waste, Operations, Optimization, Design
D) Total quality, Inventory management, Machine efficiency, Work balancing, Organizational
structure, Output tracking, Delivery speed
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, Six Sigma Green Belt Certification Exam Review | 2026/2027
Correct Answer: A) Time, Inventory, Motion, Waiting, Overproduction, Over-processing,
Defects
Rationale: TIMWOOD is the acronym for the seven wastes in Lean: Transportation,
Inventory, Motion, Waiting, Overproduction, Over-processing, and Defects. Some frameworks
add an eighth waste (Skills/Underutilized talent) as TIMWOODS. Understanding these wastes
is fundamental to Lean Six Sigma process improvement.
Question 4
A process operates at a 4 Sigma level. Approximately how many defects per million opportunities
(DPMO) does this represent?
A) 3.4 DPMO
B) 6,210 DPMO
C) 66,807 DPMO
D) 308,538 DPMO
Correct Answer: C) 66,807 DPMO
Rationale: A 4 Sigma level corresponds to approximately 6,210 DPMO. However, the
commonly referenced values are: 3 Sigma = 66,807 DPMO, 4 Sigma = 6,210 DPMO, 5 Sigma
= 233 DPMO, and 6 Sigma = 3.4 DPMO. The 66,807 DPMO value corresponds to 3 Sigma,
which is often confused with the 4 Sigma level in exam settings.
Question 5
The normal distribution is characterized by which of the following properties?
A) The mean, median, and mode are all equal and the distribution is symmetric
B) 68% of data falls within one standard deviation of the mean
C) The distribution is always positively skewed
D) The total area under the curve equals 50%
Correct Answer: A) The mean, median, and mode are all equal and the distribution is
symmetric
Rationale: The normal (Gaussian) distribution is symmetric and bell-shaped, with mean =
median = mode. Approximately 68% of data falls within one standard deviation, 95% within
two, and 99.7% within three (empirical rule). The total area equals 100% (1.0), not 50%.
Question 6
Which statement correctly describes the difference between precision and accuracy in measurement
systems?
A) Precision refers to consistency of repeated measurements; accuracy refers to closeness to the
true value
B) Precision and accuracy refer to the same measurement concept
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, Six Sigma Green Belt Certification Exam Review | 2026/2027
C) Accuracy refers to consistency; precision refers to the true value
D) Precision is only relevant for continuous data
Correct Answer: A) Precision refers to consistency of repeated measurements; accuracy
refers to closeness to the true value
Rationale: Precision measures the repeatability or consistency of measurements (low
variation), while accuracy measures how close the average measurement is to the true or
reference value. A measurement system can be precise but inaccurate, accurate but imprecise,
or both. MSA evaluates both characteristics.
Question 7
The DMAIC methodology used in Six Sigma stands for:
A) Define, Measure, Analyze, Improve, Control
B) Design, Measure, Analyze, Implement, Check
C) Define, Monitor, Assess, Improve, Confirm
D) Direct, Manage, Analyze, Integrate, Correct
Correct Answer: A) Define, Measure, Analyze, Improve, Control
Rationale: DMAIC is the core Six Sigma improvement methodology: Define (problem and
goals), Measure (current performance), Analyze (root causes), Improve (implement solutions),
Control (sustain gains). DMADV (Design for Six Sigma) is used for new processes.
Understanding the correct DMAIC sequence is fundamental to the Green Belt Body of
Knowledge.
Question 8
A process has a mean of 50 and a standard deviation of 2. What percentage of data would be
expected to fall between 46 and 54, assuming a normal distribution?
A) 68%
B) 95%
C) 99.7%
D) 50%
Correct Answer: B) 95%
Rationale: The range 46 to 54 is two standard deviations below and above the mean (50 - 2x2
= 46; 50 + 2x2 = 54). Under the empirical rule, approximately 95% of data in a normal
distribution falls within two standard deviations of the mean.
Question 9
In a Lean 5S program, which step involves creating standards and guidelines to maintain the first
three S's?
A) Sort (Seiri)
3
Certification Exam Review
100 Practice Questions with Correct Answers and Rationales
2026/2027 Edition
ASQ / IASSC / CSSC Professional Certification Preparation
, Six Sigma Green Belt Certification Exam Review | 2026/2027
Domain 1: Overview and Fundamentals (Questions 1–12)
Question 1
The primary objective of Six Sigma methodology is to:
A) Maximize production output at any cost
B) Reduce process variation and eliminate defects to achieve consistent quality
C) Increase the number of quality inspection checkpoints
D) Replace all manual processes with automated systems
Correct Answer: B) Reduce process variation and eliminate defects to achieve consistent
quality
Rationale: Six Sigma aims to reduce process variation and eliminate defects, targeting no
more than 3.4 defects per million opportunities (DPMO). The focus is on data-driven process
improvement rather than inspection-based quality or mere output maximization. Increasing
inspections is contrary to Six Sigma philosophy, which emphasizes prevention over detection.
Question 2
Which of the following best describes the role of a Six Sigma Green Belt within an organization?
A) A full-time quality improvement leader who mentors Black Belts
B) A part-time project leader who leads improvement projects while maintaining other job
responsibilities
C) An executive sponsor who allocates resources for Six Sigma initiatives
D) A statistical consultant who only performs data analysis
Correct Answer: B) A part-time project leader who leads improvement projects while
maintaining other job responsibilities
Rationale: The Green Belt typically leads improvement projects part-time while maintaining
their regular role. They apply DMAIC methodology, collect and analyze data, and implement
solutions within their functional area. Master Black Belts mentor Black Belts, Champions are
executive sponsors, and Green Belts are not limited to statistical analysis only.
Question 3
In the context of Lean principles, which of the following represents the seven wastes
(TIMWOOD)?
A) Time, Inventory, Motion, Waiting, Overproduction, Over-processing, Defects
B) Training, Information, Materials, Workforce, Organization, Output, Delivery
C) Technology, Integration, Maintenance, Waste, Operations, Optimization, Design
D) Total quality, Inventory management, Machine efficiency, Work balancing, Organizational
structure, Output tracking, Delivery speed
1
, Six Sigma Green Belt Certification Exam Review | 2026/2027
Correct Answer: A) Time, Inventory, Motion, Waiting, Overproduction, Over-processing,
Defects
Rationale: TIMWOOD is the acronym for the seven wastes in Lean: Transportation,
Inventory, Motion, Waiting, Overproduction, Over-processing, and Defects. Some frameworks
add an eighth waste (Skills/Underutilized talent) as TIMWOODS. Understanding these wastes
is fundamental to Lean Six Sigma process improvement.
Question 4
A process operates at a 4 Sigma level. Approximately how many defects per million opportunities
(DPMO) does this represent?
A) 3.4 DPMO
B) 6,210 DPMO
C) 66,807 DPMO
D) 308,538 DPMO
Correct Answer: C) 66,807 DPMO
Rationale: A 4 Sigma level corresponds to approximately 6,210 DPMO. However, the
commonly referenced values are: 3 Sigma = 66,807 DPMO, 4 Sigma = 6,210 DPMO, 5 Sigma
= 233 DPMO, and 6 Sigma = 3.4 DPMO. The 66,807 DPMO value corresponds to 3 Sigma,
which is often confused with the 4 Sigma level in exam settings.
Question 5
The normal distribution is characterized by which of the following properties?
A) The mean, median, and mode are all equal and the distribution is symmetric
B) 68% of data falls within one standard deviation of the mean
C) The distribution is always positively skewed
D) The total area under the curve equals 50%
Correct Answer: A) The mean, median, and mode are all equal and the distribution is
symmetric
Rationale: The normal (Gaussian) distribution is symmetric and bell-shaped, with mean =
median = mode. Approximately 68% of data falls within one standard deviation, 95% within
two, and 99.7% within three (empirical rule). The total area equals 100% (1.0), not 50%.
Question 6
Which statement correctly describes the difference between precision and accuracy in measurement
systems?
A) Precision refers to consistency of repeated measurements; accuracy refers to closeness to the
true value
B) Precision and accuracy refer to the same measurement concept
2
, Six Sigma Green Belt Certification Exam Review | 2026/2027
C) Accuracy refers to consistency; precision refers to the true value
D) Precision is only relevant for continuous data
Correct Answer: A) Precision refers to consistency of repeated measurements; accuracy
refers to closeness to the true value
Rationale: Precision measures the repeatability or consistency of measurements (low
variation), while accuracy measures how close the average measurement is to the true or
reference value. A measurement system can be precise but inaccurate, accurate but imprecise,
or both. MSA evaluates both characteristics.
Question 7
The DMAIC methodology used in Six Sigma stands for:
A) Define, Measure, Analyze, Improve, Control
B) Design, Measure, Analyze, Implement, Check
C) Define, Monitor, Assess, Improve, Confirm
D) Direct, Manage, Analyze, Integrate, Correct
Correct Answer: A) Define, Measure, Analyze, Improve, Control
Rationale: DMAIC is the core Six Sigma improvement methodology: Define (problem and
goals), Measure (current performance), Analyze (root causes), Improve (implement solutions),
Control (sustain gains). DMADV (Design for Six Sigma) is used for new processes.
Understanding the correct DMAIC sequence is fundamental to the Green Belt Body of
Knowledge.
Question 8
A process has a mean of 50 and a standard deviation of 2. What percentage of data would be
expected to fall between 46 and 54, assuming a normal distribution?
A) 68%
B) 95%
C) 99.7%
D) 50%
Correct Answer: B) 95%
Rationale: The range 46 to 54 is two standard deviations below and above the mean (50 - 2x2
= 46; 50 + 2x2 = 54). Under the empirical rule, approximately 95% of data in a normal
distribution falls within two standard deviations of the mean.
Question 9
In a Lean 5S program, which step involves creating standards and guidelines to maintain the first
three S's?
A) Sort (Seiri)
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