Lean Six Sigma Black Belt Certification Prep 1 — Questions and Answers
Question 1: In Measurement System Analysis (MSA), a %GR&R value greater than 30% indicates what about the measurement system?
- The system is fully acceptable for production use
- The system is marginally acceptable depending on application
- The system is unacceptable and must be improved before use (Correct answer)
- The system has insufficient discrimination between parts
Correct answer: The system is unacceptable and must be improved before use
Per AIAG MSA guidelines, %GR&R below 10% is acceptable, 10–30% may be acceptable based on the application, and above 30% means the measurement system is unacceptable — gauge variation is too large relative to total variation, making it unreliable for distinguishing good parts from bad.
Question 2: Which control chart should be used to monitor the number of defects per unit when subgroup sizes vary from sample to sample?
- c-chart
- np-chart
- p-chart
- u-chart (Correct answer)
Correct answer: u-chart
The u-chart tracks defects per unit and accommodates variable subgroup sizes, making it the correct choice when sample sizes change. The c-chart also counts defects but requires constant subgroup size. The p-chart and np-chart track the proportion or count of defective units, not defects.
Question 3: A full factorial Design of Experiment (DOE) with 4 factors each set at 2 levels requires how many experimental runs without replication?
- 8
- 12
- 16 (Correct answer)
- 32
Correct answer: 16
A 2^k full factorial design requires 2^k runs. With k = 4 factors, that is 2^4 = 16 runs. This design allows estimation of all main effects and all two-, three-, and four-way interaction effects without any confounding.
Question 4: A process yields Cp = 1.60 and Cpk = 0.75. What is the most accurate interpretation?
- The process is capable and well-centered within specification limits
- The process spread is sufficient but the mean is significantly shifted off-center (Correct answer)
- Both indices confirm the process is incapable due to excessive variation
- Cpk exceeding 1.33 confirms the process meets the Six Sigma standard
Correct answer: The process spread is sufficient but the mean is significantly shifted off-center
Cp measures potential capability based on spread alone without regard to centering. Cpk adjusts for how far the mean has drifted from the target. A high Cp with a low Cpk means the process distribution is narrow enough to fit within spec limits, but it is off-center, producing defects on one tail.
Question 5: On a Value Stream Map (VSM), what does a kaizen burst symbol represent?
- A push production trigger between upstream and downstream processes
- An area of high work-in-process inventory accumulation
- A location targeted for focused rapid improvement activity (Correct answer)
- The customer takt time demand rate at a specific process step
Correct answer: A location targeted for focused rapid improvement activity
The kaizen burst (starburst or lightning-bolt shape) is placed on a VSM to highlight areas where waste or problems have been identified and where a rapid improvement event — a kaizen workshop — should be conducted. It is an action flag, not a data symbol.
Question 6: A hypothesis test produces a p-value of 0.03 against a pre-set significance level (α) of 0.05. What is the correct conclusion?
- Fail to reject H₀; the result is not statistically significant
- Reject H₀; sufficient evidence exists to support the alternative hypothesis (Correct answer)
- The true effect size is exactly 3% above the expected value
- There is a 97% probability that the null hypothesis is true
Correct answer: Reject H₀; sufficient evidence exists to support the alternative hypothesis
When the p-value (0.03) is less than the chosen significance level α (0.05), the decision rule is to reject the null hypothesis. This indicates the observed data is unlikely under H₀, providing statistical support for the alternative. The p-value is not the probability that H₀ is true — that is a common misinterpretation.
Lean Six Sigma Black Belt Certification Prep 1
In Measurement System Analysis (MSA), a %GR&R value greater than 30% indicates what about the measurement system?