Lean Six Sigma Green Belt Certification DMAIC: Analyze Phase Techniques 3 — Questions and Answers
Question 1: A fishbone diagram is constructed and most causes cluster under the 'Methods' category. What should the team do next?
- Close the Analyze phase immediately
- Conduct a 5 Why analysis on the 'Methods' causes to find root causes (Correct answer)
- Move directly to implementing process changes
- Redesign the fishbone with fewer categories
Correct answer: Conduct a 5 Why analysis on the 'Methods' causes to find root causes
After identifying the dominant category, 5 Why analysis drills deeper into that category to identify actual root causes.
Question 2: Which assumption must be verified before using a one-way ANOVA to compare means across three process lines?
- Data must be binary
- Variances across groups must be approximately equal (Correct answer)
- Sample sizes must be identical across all groups
- The response variable must be an attribute
Correct answer: Variances across groups must be approximately equal
One-way ANOVA assumes equal variances (homoscedasticity) across groups, which should be verified with Bartlett's or Levene's test.
Question 3: A process improvement team creates a scatter plot and finds points forming a curved (non-linear) pattern. What is the BEST next step?
- Use Pearson correlation and report it as definitive
- Apply a data transformation or fit a non-linear regression model (Correct answer)
- Discard the data as invalid
- Switch to a control chart
Correct answer: Apply a data transformation or fit a non-linear regression model
When a scatter plot shows a non-linear pattern, a data transformation (e.g., log, square root) or non-linear regression model is appropriate.
Question 4: What is the primary purpose of a Failure Mode and Effects Analysis (FMEA) during the Analyze phase?
- To calculate process capability
- To prioritize potential failure modes by their Risk Priority Number (RPN) (Correct answer)
- To build a control plan for sustaining improvements
- To map the current state value stream
Correct answer: To prioritize potential failure modes by their Risk Priority Number (RPN)
FMEA identifies potential failure modes and scores them by RPN (Severity × Occurrence × Detection) to prioritize which risks to address.
Question 5: When conducting a 5 Why analysis, a team arrives at the same root cause from two different symptom branches. This most likely means:
- The analysis contains errors and must restart
- A single systemic root cause drives multiple symptom paths (Correct answer)
- The team should add more 'why' levels
- The fishbone diagram was built incorrectly
Correct answer: A single systemic root cause drives multiple symptom paths
Converging paths in a 5 Why analysis often signal a single, systemic root cause that produces multiple downstream symptoms.
Question 6: A Green Belt wants to determine whether the median cycle time differs significantly across three suppliers. Normality testing shows non-normal data. Which test is most appropriate?
- One-way ANOVA
- Kruskal-Wallis test (Correct answer)
- Two-sample t-test
- F-test for variances
Correct answer: Kruskal-Wallis test
The Kruskal-Wallis test is the non-parametric alternative to one-way ANOVA used when data is non-normal and comparing medians across three or more groups.
Question 7: In an Analyze phase tollgate review, which deliverable is MOST critical for demonstrating that root causes have been validated?
- A completed SIPOC diagram
- Statistical evidence linking X variables to Y outcomes (Correct answer)
- A finalized project charter
- A complete measurement system analysis report
Correct answer: Statistical evidence linking X variables to Y outcomes
The Analyze phase must produce data-driven, statistical evidence that identified X variables are the verified root causes of Y performance problems.
Lean Six Sigma Green Belt Certification DMAIC: Analyze Phase Techniques 3
A fishbone diagram is constructed and most causes cluster under the 'Methods' category.
What should the team do next?