Lean Six Sigma Green Belt Certification DMAIC: Measure Phase Tools 4 — Questions and Answers
Question 1: When performing a capability study, a practitioner finds the data is right-skewed. What is the BEST next step before calculating Cp and Cpk?
- Proceed with standard Cp/Cpk formulas regardless
- Transform the data or use non-normal capability analysis methods (Correct answer)
- Increase the sample size until normality is achieved
- Report the process as incapable without further analysis
Correct answer: Transform the data or use non-normal capability analysis methods
Standard Cp and Cpk formulas assume normality; skewed data requires transformation (e.g., Box-Cox) or non-normal capability methods to avoid misleading results.
Question 2: In a value stream map created during the Measure phase, 'push' production is characterized by:
- Producing only what the next step requests
- Producing based on a schedule or forecast regardless of downstream demand (Correct answer)
- Eliminating all inventory between steps
- Synchronizing all steps to takt time
Correct answer: Producing based on a schedule or forecast regardless of downstream demand
Push systems produce based on schedules or forecasts and send output downstream whether or not it is needed, often creating excess inventory (waste).
Question 3: A Green Belt calculates process cycle efficiency (PCE) as 12%. This means:
- 88% of cycle time is value-added
- Only 12% of total lead time adds value from the customer's perspective (Correct answer)
- The defect rate is 88%
- The process meets Six Sigma standards
Correct answer: Only 12% of total lead time adds value from the customer's perspective
PCE = Value-Added Time / Total Lead Time; a 12% PCE means 88% of the time the product spends in the process is non-value-added (waste).
Question 4: Which data collection tool uses a grid to tally how often different types of defects occur, enabling pattern recognition by defect type and location?
- Pareto chart
- Check sheet (Correct answer)
- Scatter diagram
- Control chart
Correct answer: Check sheet
A check sheet is a structured form used to collect and organize data about defect types, locations, or frequencies in real time at the source.
Question 5: A measurement system shows high repeatability variation. Which action would most directly address this?
- Retrain appraisers on the measurement procedure
- Recalibrate the instrument or investigate instrument condition (Correct answer)
- Increase the number of appraisers
- Use a different sampling strategy
Correct answer: Recalibrate the instrument or investigate instrument condition
Repeatability variation (same appraiser, same part, same instrument varies) typically points to the instrument itself — calibration, wear, or inconsistency in the gauge.
Question 6: What is the purpose of calculating the intraclass correlation coefficient (ICC) in a measurement system analysis?
- To determine if two variables are linearly correlated
- To assess the reliability of the measurement system by comparing measurement variation to total variation (Correct answer)
- To calculate the sigma level of the process
- To verify that the data follows a normal distribution
Correct answer: To assess the reliability of the measurement system by comparing measurement variation to total variation
ICC quantifies how much of the observed variation is due to real differences between items rather than measurement error, indicating measurement system reliability.
Question 7: A team is measuring cycle time for a loan approval process. The data has extreme outliers on the high end. Which measure of central tendency should they report as most representative?
- Mean
- Median (Correct answer)
- Mode
- Range
Correct answer: Median
The median is resistant to extreme outliers, making it a better measure of central tendency than the mean when data is heavily skewed or has extreme values.
Lean Six Sigma Green Belt Certification DMAIC: Measure Phase Tools 4
When performing a capability study, a practitioner finds the data is right-skewed.
What is the BEST next step before calculating Cp and Cpk?