Lean Six Sigma Black Belt Certification Lean Six Sigma Black Belt Define and Measure Phases 1 — Questions and Answers
Question 1: A Black Belt wants to visually display the sequence of steps in a customer order fulfillment process, including handoffs between departments and wait times. Which tool is most appropriate?
- Value Stream Map (Correct answer)
- Cause-and-Effect Diagram
- Control Chart
- Affinity Diagram
Correct answer: Value Stream Map
A Value Stream Map (VSM) captures material and information flow, process steps, cycle times, and wait times across departments, making it ideal for identifying non-value-added activities during the Define/Measure phases.
Question 2: During the Measure phase, a Black Belt collects 25 subgroups of 5 samples each to establish process baselines. Which control chart pair is most appropriate for monitoring the process mean and variation?
- X-bar and R chart (Correct answer)
- p-chart and np-chart
- c-chart and u-chart
- I-MR chart
Correct answer: X-bar and R chart
The X-bar and R chart is the standard choice for subgroup data with a fixed sample size (n=2–10), tracking both the subgroup mean (X-bar) and range (R) to monitor central tendency and spread simultaneously.
Question 3: A project charter is being reviewed and the team notices the problem statement reads: 'We need to implement a new ERP system to fix customer complaints.' What is wrong with this statement?
- It presupposes a solution rather than describing the problem objectively (Correct answer)
- It lacks a measurable baseline metric
- It does not identify the project sponsor
- It fails to state the project timeline
Correct answer: It presupposes a solution rather than describing the problem objectively
A well-written problem statement describes what is wrong and its impact without prescribing a solution. Jumping to 'implement an ERP system' closes off root-cause analysis before the DMAIC process has even begun.
Question 4: A Black Belt performs a Gauge R&R study and finds that %Gauge R&R is 28%. How should this measurement system be classified?
- Marginally acceptable — use with caution and consider improvement (Correct answer)
- Acceptable — the system is fit for purpose
- Unacceptable — the measurement system must be replaced before proceeding
- Excellent — variation is well within industry benchmarks
Correct answer: Marginally acceptable — use with caution and consider improvement
Industry guidelines classify %Gauge R&R below 10% as acceptable, 10–30% as marginal (may be acceptable depending on application), and above 30% as unacceptable. At 28%, the system falls in the marginal zone, warranting caution.
Question 5: Which formula correctly expresses process yield in terms of Defects Per Unit (DPU) for a Poisson-distributed defect model?
- Y = e^(−DPU) (Correct answer)
- Y = 1 − DPU
- Y = DPU / Opportunities
- Y = (1 − DPU)^n
Correct answer: Y = e^(−DPU)
Assuming Poisson distribution of defects, the first-pass yield is Y = e^(−DPU). This formula is foundational for calculating Rolled Throughput Yield (RTY) across multiple process steps.
Question 6: A Black Belt is selecting a sampling strategy to estimate the average transaction time across 12 regional call centers. The Black Belt suspects significant variation between centers but relative homogeneity within each center. Which sampling method is most appropriate?
- Stratified random sampling (Correct answer)
- Simple random sampling
- Systematic sampling
- Convenience sampling
Correct answer: Stratified random sampling
Stratified random sampling divides the population into homogeneous subgroups (strata — here, the 12 centers) and samples randomly within each, ensuring each stratum is represented and reducing overall variance in the estimate.
Lean Six Sigma Black Belt Certification Lean Six Sigma Black Belt Define and Measure Phases 1
A Black Belt wants to visually display the sequence of steps in a customer order fulfillment process, including handoffs between departments and wait times.
Which tool is most appropriate?