CLL Data Analysis & Reporting 2 — Questions and Answers
Question 1: Which statistical measure is most useful for identifying the spread of process data around its mean?
- Median
- Mode
- Standard deviation (Correct answer)
- Range midpoint
Correct answer: Standard deviation
Standard deviation quantifies how much individual data points deviate from the mean, making it the primary measure of process spread.
Question 2: A Lean team notices their defect rate data forms a J-shaped distribution. What does this most likely indicate?
- The process is centered on target
- Rare events dominate the data (Correct answer)
- Data was collected incorrectly
- The process has multiple shift patterns
Correct answer: Rare events dominate the data
A J-shaped distribution typically indicates rare-event data where most values cluster near zero with a long tail, common in defect counts.
Question 3: What is the primary purpose of a control chart's upper and lower control limits (UCL/LCL)?
- Define customer specification boundaries
- Indicate when a process has shifted to special cause variation (Correct answer)
- Set production targets for operators
- Replace the need for process audits
Correct answer: Indicate when a process has shifted to special cause variation
UCL and LCL are statistically derived at ±3 sigma to signal when special cause variation has entered the process.
Question 4: In a Lean data reporting cadence, what is the recommended frequency for reviewing operational KPIs on a visual management board?
- Monthly during management reviews
- Weekly during team meetings only
- Daily at shift start or standup (Correct answer)
- Quarterly during strategic planning
Correct answer: Daily at shift start or standup
Daily review of KPIs on visual management boards enables rapid detection and response to problems before they escalate.
Question 5: A process capability index of Cpk = 0.85 tells a Lean analyst that:
- The process is highly capable and centered
- The process does not meet the minimum capability threshold of 1.0 (Correct answer)
- The process mean equals the specification target
- The process has no special cause variation
Correct answer: The process does not meet the minimum capability threshold of 1.0
A Cpk below 1.0 indicates the process is not capable of consistently producing output within specification limits.
Question 6: Which chart type is best suited for displaying the relative contribution of each defect category to the total defect count?
- Scatter diagram
- Run chart
- Pareto chart (Correct answer)
- Box plot
Correct answer: Pareto chart
A Pareto chart ranks defect categories by frequency with a cumulative percentage line, highlighting the vital few causes.
Question 7: When conducting a measurement system analysis (MSA), a high % Gauge R&R result (>30%) suggests:
- The measurement system is acceptable for production use
- Measurement variation is excessive and the gauge needs improvement (Correct answer)
- The process has too much part-to-part variation
- Operators are performing the measurement correctly
Correct answer: Measurement variation is excessive and the gauge needs improvement
A Gauge R&R above 30% means the measurement system contributes too much variation and will mask real process signals.
CLL Data Analysis & Reporting 2
Which statistical measure is most useful for identifying the spread of process data around its mean?