Lean Six Sigma Green Belt Certification Measure Phase and Statistics 5 — Questions and Answers
Question 1: What is the purpose of a box plot (box-and-whisker plot) in data analysis?
- To display frequency of defect categories
- To show the five-number summary and identify outliers (Correct answer)
- To track process performance over time
- To compare planned versus actual results
Correct answer: To show the five-number summary and identify outliers
A box plot displays the minimum, Q1, median, Q3, and maximum, providing a visual summary of distribution shape and outliers.
Question 2: During the Measure phase, a SIPOC diagram is primarily used to:
- Calculate process sigma level
- Identify measurement system errors
- Provide a high-level view of the process and its boundaries (Correct answer)
- Determine sample size requirements
Correct answer: Provide a high-level view of the process and its boundaries
SIPOC maps Suppliers, Inputs, Process, Outputs, and Customers to establish scope and context before detailed measurement begins.
Question 3: Which term describes the smallest detectable difference that a measurement instrument can reliably distinguish?
- Calibration
- Resolution (discrimination) (Correct answer)
- Linearity
- Stability
Correct answer: Resolution (discrimination)
Resolution (or discrimination) is the smallest increment a gauge can detect; it should be at least 1/10 of the total process variation.
Question 4: A process collects data at regular intervals regardless of lot boundaries. This describes which sampling method?
- Stratified sampling
- Cluster sampling
- Systematic sampling (Correct answer)
- Judgment sampling
Correct answer: Systematic sampling
Systematic sampling selects every nth unit at fixed intervals, making it time- or production-based rather than random at each draw.
Question 5: If a process has a long-term sigma level of 3.0, what is the approximate DPMO?
- 66,807 (Correct answer)
- 3,400
- 233
- 6,210
Correct answer: 66,807
A 3-sigma process (long-term, with 1.5σ shift) corresponds to approximately 66,807 DPMO.
Question 6: What is the interquartile range (IQR) used to measure?
- The total range of the dataset
- The spread of the middle 50% of data (Correct answer)
- The distance between the mean and median
- The frequency of values near the center
Correct answer: The spread of the middle 50% of data
IQR = Q3 - Q1, capturing the spread of the central 50% of the data while ignoring extreme values.
Question 7: In a measurement system analysis, 'linearity' refers to:
- Consistency of measurements over time
- Variation in bias across the operating range of the gauge (Correct answer)
- Agreement between different operators
- The ability to detect small incremental changes
Correct answer: Variation in bias across the operating range of the gauge
Linearity assesses whether the gauge bias is consistent across all values in its expected operating range.
Lean Six Sigma Green Belt Certification Measure Phase and Statistics 5
What is the purpose of a box plot (box-and-whisker plot) in data analysis?