Lean Six Sigma Black Belt Certification Assessment 5 — Questions and Answers
Question 1: A Black Belt assessing a manufacturing process finds OEE of 48%. Which three OEE components multiply to produce this score?
- Availability × Performance × Quality (Correct answer)
- Uptime × Throughput × Yield
- Reliability × Efficiency × Defect Rate
- Cycle Time × Demand Rate × First-Pass Yield
Correct answer: Availability × Performance × Quality
OEE = Availability (planned uptime actually running) × Performance (actual vs. ideal speed) × Quality (good parts vs. total parts produced).
Question 2: During process assessment a team finds that the measurement system's linearity is poor. What does poor linearity indicate?
- The bias of the measurement system changes across the operating range (Correct answer)
- The measurement system has inconsistent repeatability between operators
- The gage systematically reads too high across all measurement values
- The measurement system cannot distinguish between consecutive measurements
Correct answer: The bias of the measurement system changes across the operating range
Linearity measures how consistent the bias is across the full range of expected measurements; poor linearity means the instrument's accuracy varies depending on where in the range you measure.
Question 3: When assessing process stability using a control chart, which pattern suggests a special cause related to a gradual process drift or tool wear?
- Six or more consecutive points trending in one direction (Correct answer)
- Two out of three consecutive points beyond two sigma from the centerline
- One point beyond the three-sigma control limit
- Fifteen consecutive points within one sigma of the centerline on both sides
Correct answer: Six or more consecutive points trending in one direction
A sustained trend of six or more consecutive points moving in one direction is a Nelson/Western Electric rule that signals a gradual shift—often caused by wear, fatigue, or drift.
Question 4: A Black Belt uses a cause-and-effect matrix (C&E matrix) to prioritize inputs for further data collection. The matrix scores each process input against:
- Customer output requirements weighted by their importance rating (Correct answer)
- Control chart violation rules weighted by detection difficulty
- Cost of poor quality weighted by defect frequency
- FMEA severity scores weighted by occurrence ratings
Correct answer: Customer output requirements weighted by their importance rating
The C&E matrix scores each process input (X) for its impact on each customer-critical output (Y), weighted by the customer's importance rating for that output.
Question 5: Which type of sampling is most appropriate when a process runs in natural groups (e.g., shifts, machines) and the Black Belt wants each group represented proportionally?
- 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) and samples proportionally from each, ensuring all sources of variation are represented.
Question 6: During baseline data collection, a Black Belt discovers the data contains outliers due to measurement errors. What is the appropriate action before computing capability metrics?
- Investigate and document each outlier; remove only those confirmed to be measurement errors (Correct answer)
- Remove all points beyond two standard deviations automatically
- Retain all data points to preserve statistical integrity
- Transform the data using Box-Cox to make outliers insignificant
Correct answer: Investigate and document each outlier; remove only those confirmed to be measurement errors
Outliers should be individually investigated; only confirmed measurement or recording errors may be removed—legitimate process events must remain in the dataset.
Question 7: A Black Belt calculates the Cost of Poor Quality (COPQ) for a process during assessment. Which of the following is a category of internal failure cost?
- Scrap and rework before product reaches the customer (Correct answer)
- Warranty repair after product delivery
- Inspection and test labor costs
- Supplier qualification audits
Correct answer: Scrap and rework before product reaches the customer
Internal failure costs are incurred when defects are found before the product reaches the customer; scrap and rework are the primary examples.
Lean Six Sigma Black Belt Certification Assessment 5
A Black Belt assessing a manufacturing process finds OEE of 48%.
Which three OEE components multiply to produce this score?