Lean Six Sigma Yellow Belt Certification The Measure Phase 4 — Questions and Answers
Question 1: In the context of the Measure phase, 'operational definitions' are important because they:
- Define the project timeline
- Ensure everyone measures the same thing consistently (Correct answer)
- Set the financial targets for the project
- Identify root causes of variation
Correct answer: Ensure everyone measures the same thing consistently
Operational definitions provide precise, agreed-upon descriptions of what is being measured so all collectors gather data the same way.
Question 2: Which chart is most appropriate for monitoring the proportion of defective items when subgroup sizes vary?
- p-chart (Correct answer)
- c-chart
- np-chart
- u-chart
Correct answer: p-chart
The p-chart tracks the proportion (fraction) of defective items and accommodates variable subgroup sizes, unlike the np-chart which requires constant subgroup size.
Question 3: A process has a mean of 50 and standard deviation of 2. The specification limits are 44 to 56. What is the Cp value?
- 1.00 (Correct answer)
- 1.50
- 2.00
- 0.75
Correct answer: 1.00
Cp = (USL - LSL) / (6σ) = (56 - 44) / (6 × 2) = 12 / 12 = 1.00.
Question 4: What is the main limitation of using a histogram alone to assess process capability?
- It cannot display the mean
- It does not reveal the time sequence of data, masking instability (Correct answer)
- It requires attribute data
- It cannot show specification limits
Correct answer: It does not reveal the time sequence of data, masking instability
A histogram collapses all time information, so it cannot reveal shifts, trends, or special causes that a time-ordered control chart would detect.
Question 5: Which of the following best describes 'measurement system bias'?
- Random scatter around the true value
- A consistent, systematic offset between measured and true values (Correct answer)
- Variation between operators
- Variation over repeated measurements by one operator
Correct answer: A consistent, systematic offset between measured and true values
Bias (accuracy error) is the difference between the average measured value and the true (reference) value, indicating a systematic shift.
Question 6: In process capability analysis, what does a Cpk value of less than 1.0 indicate?
- The process is perfectly centered
- The process is producing defects beyond one or both specification limits (Correct answer)
- The process has only common cause variation
- The measurement system is inadequate
Correct answer: The process is producing defects beyond one or both specification limits
A Cpk below 1.0 means the process spread extends beyond at least one specification limit, resulting in defective output.
Question 7: When conducting a Pareto analysis on defect data, the '80/20 rule' suggests that:
- 80% of the process steps add value
- 80% of defects come from approximately 20% of the causes (Correct answer)
- 80% of measurement error is due to operators
- 20% of customers cause 80% of complaints
Correct answer: 80% of defects come from approximately 20% of the causes
The Pareto principle states that roughly 80% of problems stem from about 20% of causes, guiding teams to focus on the vital few issues.
Lean Six Sigma Yellow Belt Certification The Measure Phase 4
In the context of the Measure phase, 'operational definitions' are important because they: