Lean Six Sigma Green Belt Certification Knowledge 4 — Questions and Answers
Question 1: Which phase of DMAIC is primarily responsible for implementing and validating solutions?
- Measure
- Analyze
- Improve (Correct answer)
- Control
Correct answer: Improve
The Improve phase develops, pilots, and implements solutions that address confirmed root causes identified in the Analyze phase.
Question 2: In Design of Experiments (DOE), a full factorial design with 3 factors at 2 levels requires how many experimental runs?
- 6
- 8 (Correct answer)
- 9
- 12
Correct answer: 8
A full 2^3 factorial design requires 2³ = 8 runs to test all combinations of 3 factors at 2 levels each.
Question 3: What is the key distinction between common cause variation and special cause variation?
- Common cause is larger in magnitude than special cause
- Common cause is inherent to the process; special cause is from an external, assignable factor (Correct answer)
- Special cause can only be detected with attribute data
- Common cause always requires process redesign to eliminate
Correct answer: Common cause is inherent to the process; special cause is from an external, assignable factor
Common cause variation is the natural, random variation built into a stable process, while special cause variation is due to identifiable, non-routine factors.
Question 4: A Gage R&R study reveals that measurement system variation accounts for 35% of total observed variation. This result indicates:
- The measurement system is acceptable for process control
- The measurement system needs improvement before data can be trusted (Correct answer)
- The process has high variation compared to spec limits
- Repeatability is worse than reproducibility
Correct answer: The measurement system needs improvement before data can be trusted
AIAG guidelines classify a measurement system contributing >30% of total variation as unacceptable and requiring corrective action before use.
Question 5: Which of the following is an example of a 'mistake-proofing' (poka-yoke) device?
- A statistical process control chart posted on the shop floor
- A USB connector that can only be inserted in the correct orientation (Correct answer)
- A checklist completed after each assembly step
- A training manual for new employees
Correct answer: A USB connector that can only be inserted in the correct orientation
A USB connector's physical design prevents incorrect insertion, making the error physically impossible — a classic poka-yoke that prevents defects at the source.
Question 6: In regression analysis, what does the R-squared (R²) value represent?
- The slope of the regression line
- The correlation coefficient between two variables
- The proportion of variation in Y explained by the model (Correct answer)
- The statistical significance of the regression equation
Correct answer: The proportion of variation in Y explained by the model
R² measures the proportion of variability in the response variable (Y) that is explained by the predictor variable(s) in the regression model.
Question 7: The concept of 'Gemba' in Lean Six Sigma refers to:
- A structured brainstorming technique
- The actual place where work is performed (Correct answer)
- A visual management board
- A cross-functional improvement team
Correct answer: The actual place where work is performed
Gemba is Japanese for 'the real place' — in Lean, it means going to the shop floor or actual work location to observe processes directly.
Lean Six Sigma Green Belt Certification Knowledge 4
Which phase of DMAIC is primarily responsible for implementing and validating solutions?