Lean Six Sigma Green Belt Certification Assessment 5 — Questions and Answers
Question 1: A Green Belt is assessing whether a process change has had a statistically significant impact on defect rates. Before the change: 45 defects in 500 units. After: 20 defects in 500 units. Which test is most appropriate?
- Two-sample t-test
- Two-proportion z-test (Correct answer)
- Paired t-test
- One-sample z-test
Correct answer: Two-proportion z-test
Comparing two proportions (defect rates) from two independent samples before and after a change requires a two-proportion z-test.
Question 2: During a Lean assessment, a team identifies buffer inventory between process steps. This inventory is classified as which type of waste?
- Overprocessing
- Overproduction
- Inventory (Correct answer)
- Transportation
Correct answer: Inventory
Excess buffer or work-in-process inventory between steps is classified as inventory waste, one of the original seven wastes (muda) in Lean thinking.
Question 3: A Green Belt assesses whether cycle time data follows a normal distribution before performing capability analysis. Which tool is most appropriate for this assessment?
- Pareto chart
- Probability plot (normal probability plot) (Correct answer)
- Run chart
- Scatter diagram
Correct answer: Probability plot (normal probability plot)
A normal probability plot (also called a normal plot or Q-Q plot) graphically assesses whether data follows a normal distribution by checking how closely points follow a straight line.
Question 4: In a Lean Six Sigma project assessment, the team is reviewing the Analyze phase outputs. Which deliverable confirms the project has correctly identified root causes before moving to Improve?
- An updated SIPOC diagram
- A validated fishbone with statistical evidence linking Xs to Ys (Correct answer)
- A completed process map of the future state
- A control plan with monitoring frequencies
Correct answer: A validated fishbone with statistical evidence linking Xs to Ys
Moving from Analyze to Improve requires validated root causes where statistical analysis has confirmed the relationship between input variables (Xs) and output measures (Ys).
Question 5: A Green Belt assesses the results of a designed experiment (DOE). A main effects plot shows a steep slope for Factor A and a nearly flat line for Factor B. This indicates:
- Factor B has a larger effect on the response than Factor A
- Factor A has a larger effect on the response than Factor B (Correct answer)
- Both factors have equal and significant effects
- Neither factor significantly influences the response
Correct answer: Factor A has a larger effect on the response than Factor B
In a main effects plot, steeper slopes indicate greater impact on the response variable; Factor A's steep slope shows it has a much larger effect than Factor B.
Question 6: When assessing a completed Six Sigma project, the sponsor asks for a post-project audit at 6 months. What is the primary purpose of this audit?
- To identify new problems to start a new project
- To verify that gains have been sustained and the control plan is effective (Correct answer)
- To train new team members on the original project methodology
- To recalculate the original baseline sigma level
Correct answer: To verify that gains have been sustained and the control plan is effective
A post-project audit verifies that improvements have been sustained over time and that the control plan is being followed and is effective in maintaining the gains.
Question 7: A Green Belt is assessing the prioritization matrix output. The team has scored potential improvements on impact and effort. Which quadrant should be implemented first?
- High effort, high impact
- Low effort, low impact
- High effort, low impact
- Low effort, high impact (Correct answer)
Correct answer: Low effort, high impact
Low effort, high impact improvements (often called 'quick wins' or 'low-hanging fruit') should be prioritized first as they deliver maximum value for minimal resource investment.
Lean Six Sigma Green Belt Certification Assessment 5
A Green Belt is assessing whether a process change has had a statistically significant impact on defect rates.
Before the change: 45 defects in 500 units.
After: 20 defects in 500 units.
Which test is most appropriate?