Lean Six Sigma Green Belt Certification Assessment 4 — Questions and Answers
Question 1: A Green Belt assesses a supplier's delivery performance using a p-chart. The chart shows the process is in control with an average defective rate of 4%. This means:
- The process is performing at an acceptable level and needs no attention
- The process is stable and predictable at the current 4% defective rate (Correct answer)
- The process is out of control and requires immediate corrective action
- The 4% rate is statistically insignificant and can be ignored
Correct answer: The process is stable and predictable at the current 4% defective rate
An in-control process on a p-chart is stable and predictable; while the 4% rate may not be acceptable, it is consistent — improvement requires a fundamental process change, not firefighting.
Question 2: When assessing the potential impact of process inputs, a Green Belt uses FMEA. The Risk Priority Number (RPN) is calculated as:
- Severity × Occurrence × Detection (Correct answer)
- Severity + Occurrence + Detection
- Severity × Occurrence / Detection
- (Severity + Occurrence) × Detection
Correct answer: Severity × Occurrence × Detection
RPN = Severity × Occurrence × Detection, where each factor is rated 1-10, giving a maximum RPN of 1,000 to prioritize corrective actions.
Question 3: A Green Belt is assessing whether two process improvement ideas produce statistically different results. Which statistical test is most appropriate when comparing the means of two independent groups with continuous data?
- Chi-square test
- Two-sample t-test (Correct answer)
- One-proportion z-test
- Mann-Whitney test for paired samples
Correct answer: Two-sample t-test
A two-sample t-test compares the means of two independent groups with continuous data to determine if the difference is statistically significant.
Question 4: During a process assessment, the team discovers that 80% of defects come from 20% of the causes. Which tool visually demonstrates this relationship?
- Histogram
- Pareto chart (Correct answer)
- Scatter plot
- Box plot
Correct answer: Pareto chart
A Pareto chart displays defects or causes in descending order with a cumulative percentage line, visually illustrating the 80/20 principle for prioritization.
Question 5: A Green Belt performs a linear regression as part of process assessment. The R² value is 0.92. What does this indicate?
- 92% of the variation in Y is explained by the regression model (Correct answer)
- The model predicts correctly 92% of the time
- The correlation coefficient between X and Y is 0.92
- 92% of data points fall within the confidence interval
Correct answer: 92% of the variation in Y is explained by the regression model
R² (coefficient of determination) represents the proportion of variance in the dependent variable (Y) that is explained by the independent variable(s) in the regression model.
Question 6: A team assessing a transactional process uses process cycle efficiency (PCE). A PCE of 15% means:
- 85% of the process cycle is value-added time
- Only 15% of total lead time is value-added time (Correct answer)
- The defect rate is 85%
- The process requires 15% overtime to complete
Correct answer: Only 15% of total lead time is value-added time
PCE = Value-Added Time / Total Lead Time × 100; a PCE of 15% means only 15% of the total elapsed time actually adds value for the customer.
Question 7: When assessing measurement system bias, a Green Belt compares instrument readings to a known reference value. This assessment is called:
- Linearity study
- Stability study
- Accuracy/bias study (Correct answer)
- Repeatability study
Correct answer: Accuracy/bias study
A bias (accuracy) study determines the difference between the average measurement from a gauge and the true (reference) value of the measured characteristic.
Lean Six Sigma Green Belt Certification Assessment 4
A Green Belt assesses a supplier's delivery performance using a p-chart.
The chart shows the process is in control with an average defective rate of 4%.
This means: