Lean Six Sigma Green Belt Certification Knowledge 5 — Questions and Answers
Question 1: Which control chart is most appropriate for monitoring individual measurements when subgroup sizes equal 1?
- X-bar and R chart
- p-chart
- Individuals and Moving Range (I-MR) chart (Correct answer)
- c-chart
Correct answer: Individuals and Moving Range (I-MR) chart
The I-MR chart monitors individual data points and uses moving ranges between consecutive points to estimate process variation when only one measurement is taken at a time.
Question 2: A project charter defines the problem statement, scope, goals, and team. Which element is most critical to include to ensure project boundaries are respected?
- Business case
- Scope statement (Correct answer)
- Team roles
- Milestone timeline
Correct answer: Scope statement
The scope statement explicitly defines what is included and excluded from the project, preventing scope creep and keeping the team focused on the right problem.
Question 3: In a cause-and-effect (fishbone) diagram, the 'bones' typically represent which categories?
- Plan, Do, Check, Act
- Man, Machine, Method, Material, Measurement, Environment (Correct answer)
- Suppliers, Inputs, Process, Outputs, Customers
- Define, Measure, Analyze, Improve, Control
Correct answer: Man, Machine, Method, Material, Measurement, Environment
The 6M categories (Man, Machine, Method, Material, Measurement, Environment) form the main branches of a fishbone diagram to systematically explore root causes.
Question 4: What is the primary goal of a control plan in the Control phase of DMAIC?
- To document the root causes found during analysis
- To provide a roadmap for sustaining process improvements after the project closes (Correct answer)
- To calculate the financial benefits of the project
- To identify new improvement opportunities for future projects
Correct answer: To provide a roadmap for sustaining process improvements after the project closes
A control plan specifies the monitoring methods, response plans, and responsibilities needed to sustain improvements and prevent reversion to old process behavior.
Question 5: When conducting a multi-vari study, the Green Belt is looking to understand:
- The relationship between two continuous variables
- The sources and patterns of variation (positional, cyclical, temporal) (Correct answer)
- Whether two population means are statistically different
- The capability of the measurement system
Correct answer: The sources and patterns of variation (positional, cyclical, temporal)
Multi-vari charts graphically display three families of variation — positional, cyclical, and temporal — to narrow down which family contributes most to the observed variation.
Question 6: A Green Belt wants to test whether a process improvement changed the defect rate. Which test is most appropriate for comparing two proportions?
- Two-sample t-test
- One-way ANOVA
- Two-proportion z-test (Correct answer)
- Paired t-test
Correct answer: Two-proportion z-test
The two-proportion z-test determines whether there is a statistically significant difference between two independent proportions, such as defect rates before and after improvement.
Question 7: In Lean, the 'spaghetti diagram' is used primarily to:
- Map the flow of information between departments
- Visualize the physical movement of people or materials through a workspace (Correct answer)
- Display the sequence of process steps in a swimlane format
- Identify which process steps add value to the customer
Correct answer: Visualize the physical movement of people or materials through a workspace
A spaghetti diagram traces the actual physical path traveled by a person, product, or material, revealing excessive motion waste and layout inefficiencies.
Lean Six Sigma Green Belt Certification Knowledge 5
Which control chart is most appropriate for monitoring individual measurements when subgroup sizes equal 1?