Certified Six Sigma Black Belt Exam Certified Six Sigma Black Belt MCQ 5 — Questions and Answers
Question 1: What does a Weibull shape parameter (β) less than 1 indicate about a product's failure pattern?
- Wear-out failures increasing over time
- Random failures with constant hazard rate
- Infant mortality — decreasing failure rate over time (Correct answer)
- No failures within the warranty period
Correct answer: Infant mortality — decreasing failure rate over time
β < 1 in the Weibull distribution indicates decreasing failure rate, characteristic of early-life or infant mortality failures.
Question 2: Which mistake-proofing (poka-yoke) method prevents an error from being passed to the next operation?
- Warning method
- Shutdown method
- Control method (Correct answer)
- Detection method
Correct answer: Control method
The control method physically prevents the defect from moving forward, while warning methods only alert the operator.
Question 3: In ANOVA, the F-statistic is calculated as:
- Within-group variance / Between-group variance
- Between-group variance / Within-group variance (Correct answer)
- Total variance / Sample size
- Residual sum of squares / Total sum of squares
Correct answer: Between-group variance / Within-group variance
The F-statistic is the ratio of between-group (treatment) mean square to within-group (error) mean square.
Question 4: When calculating process sigma level, a 1.5 sigma shift is typically applied because:
- It is required by ISO 9001
- Long-term processes drift up to 1.5σ from their short-term mean (Correct answer)
- It simplifies the DPMO calculation
- It compensates for measurement system error
Correct answer: Long-term processes drift up to 1.5σ from their short-term mean
Motorola's empirical finding is that processes shift up to ±1.5σ over time due to factors like tool wear and material variation.
Question 5: A Black Belt is conducting a DOE and wants to estimate the effect of a two-factor interaction. What is the minimum number of runs required?
- 2
- 4 (Correct answer)
- 6
- 8
Correct answer: 4
A 2^2 full factorial (4 runs) is the minimum to estimate main effects and a two-factor interaction with two factors.
Question 6: Which quality cost category includes the cost of scrap, rework, and warranty repairs?
- Prevention costs
- Appraisal costs
- Internal failure costs (for scrap/rework) and external failure costs (for warranty) (Correct answer)
- Opportunity costs
Correct answer: Internal failure costs (for scrap/rework) and external failure costs (for warranty)
Scrap and rework are internal failure costs (before delivery); warranty repairs are external failure costs (after delivery).
Question 7: In a transfer function Y = f(X), what does the Black Belt's role in Six Sigma primarily focus on?
- Optimizing Y directly through inspection
- Identifying and controlling the critical Xs that drive Y (Correct answer)
- Eliminating all Xs to reduce variation
- Increasing the number of Ys monitored
Correct answer: Identifying and controlling the critical Xs that drive Y
Six Sigma's core principle is that outputs (Y) are determined by inputs/process variables (X), so improvement comes from managing the Xs.
Certified Six Sigma Black Belt Exam Certified Six Sigma Black Belt MCQ 5
What does a Weibull shape parameter (β) less than 1 indicate about a product's failure pattern?