Lean Six Sigma Green Belt Certification Analyze Phase Tools 5 — Questions and Answers
Question 1: What is the primary goal of a 5 Whys analysis in the Analyze phase?
- To prioritize defects by their financial impact
- To drill down from a symptom to its underlying root cause through iterative questioning (Correct answer)
- To calculate the probability of failure for each cause
- To map all possible causes using a fishbone structure
Correct answer: To drill down from a symptom to its underlying root cause through iterative questioning
The 5 Whys technique repeatedly asks 'why' to move past symptoms and surface the true root cause of a problem.
Question 2: A team runs a normality test (Anderson-Darling) and gets p = 0.023. At α = 0.05, what should the team conclude?
- The data is normally distributed; proceed with parametric tests
- The data is not normally distributed; consider non-parametric methods or transformations (Correct answer)
- The sample size is too small to determine normality
- The process is out of control
Correct answer: The data is not normally distributed; consider non-parametric methods or transformations
Since p (0.023) < α (0.05), the null hypothesis of normality is rejected, indicating the data does not follow a normal distribution.
Question 3: In a value stream map used during the Analyze phase, what does the 'push' arrow symbol indicate?
- Material pulled based on downstream customer demand
- Material or information pushed to the next step regardless of downstream needs (Correct answer)
- A kaizen improvement burst opportunity
- Electronic information flow between steps
Correct answer: Material or information pushed to the next step regardless of downstream needs
A push arrow in a VSM represents material being moved to the next process step based on a schedule or upstream production, not actual demand.
Question 4: Which regression diagnostic plot should a Green Belt examine to check whether residuals are randomly distributed (a key regression assumption)?
- Normal probability plot of residuals (Correct answer)
- Histogram of X values
- Scatter plot of Y vs. X
- Box plot of Y by group
Correct answer: Normal probability plot of residuals
The normal probability plot (or residuals vs. fitted values plot) checks whether residuals are randomly and normally distributed around zero.
Question 5: A Green Belt wants to confirm that a suspected root cause actually explains the defects, not just correlates with them. Which approach best supports causal inference in the Analyze phase?
- Increase sample size until p < 0.05
- Validate the cause-effect relationship through a controlled experiment or stratified data analysis (Correct answer)
- Use a Pareto chart to confirm the cause ranks highest in frequency
- Accept any cause with r > 0.7 in a scatter plot
Correct answer: Validate the cause-effect relationship through a controlled experiment or stratified data analysis
Correlation alone does not establish causation; a controlled experiment or stratified analysis where the suspected X is deliberately varied provides causal evidence.
Question 6: A team applies the SIPOC in the Analyze phase to trace a defect. Which element of SIPOC is most useful for identifying the source of a faulty input?
- Output
- Customer
- Supplier (Correct answer)
- Process step
Correct answer: Supplier
The Supplier element identifies who or what provides each input, making it the starting point for tracing faulty inputs to their origin.
Question 7: When using a Pugh concept selection matrix during the Analyze phase, what does a datum (baseline) represent?
- The concept with the highest weighted score
- The current process or reference concept against which alternatives are compared (Correct answer)
- The concept eliminated in the first round of screening
- The customer requirement with the highest importance rating
Correct answer: The current process or reference concept against which alternatives are compared
The datum is a reference point (usually the current state or a known benchmark) used to rate all alternative concepts as better (+), worse (−), or same (S).
Lean Six Sigma Green Belt Certification Analyze Phase Tools 5
What is the primary goal of a 5 Whys analysis in the Analyze phase?