Lean Six Sigma Green Belt Certification Control Phase and Sustainment 4 — Questions and Answers
Question 1: A sustained improvement in a transactional process is BEST evidenced by:
- The team's subjective assessment that the process feels smoother
- A statistically significant shift in the process output metric sustained over 3-6 months post-implementation (Correct answer)
- A one-time measurement showing the new process meets the target
- Management approval of the new standard operating procedure
Correct answer: A statistically significant shift in the process output metric sustained over 3-6 months post-implementation
True sustainment requires demonstrating that the improved performance has been maintained over a meaningful time horizon with statistical evidence, not just at a single point in time.
Question 2: What does it mean when an individuals (I) chart shows a point outside the upper control limit (UCL)?
- The process specification has been violated
- A special cause of variation has likely occurred (Correct answer)
- The measurement system needs recalibration
- The control limits need to be widened
Correct answer: A special cause of variation has likely occurred
A point outside the UCL on an individuals chart signals that a special cause has likely shifted the process, requiring investigation to identify and eliminate the root cause.
Question 3: Which of the following BEST describes the purpose of a lessons-learned document in the Control phase?
- To formally close the project with finance sign-off
- To capture knowledge from the project so future teams can avoid similar problems and replicate successes (Correct answer)
- To document all the data collected during the Measure phase
- To update the team's FMEA with new risk scores
Correct answer: To capture knowledge from the project so future teams can avoid similar problems and replicate successes
A lessons-learned document captures what worked, what did not, and key insights so that organizational knowledge is retained and future projects benefit from the experience.
Question 4: A team is choosing between a p chart and a c chart. The deciding factor is:
- Whether the process is continuous or discrete
- Whether they are counting defectives (units) or defects (per unit) (Correct answer)
- Whether the sample size is fixed or variable
- Whether the process is in manufacturing or services
Correct answer: Whether they are counting defectives (units) or defects (per unit)
A c chart tracks the count of defects per inspection unit (multiple defects possible per unit), while a p chart tracks the proportion of defective units (a unit is either defective or not).
Question 5: The concept of 'process entitlement' in capability analysis refers to:
- The minimum capability the process must achieve to meet customer needs
- The best short-term capability the process has demonstrated under ideal conditions (Correct answer)
- The average capability over a 12-month baseline period
- The capability target agreed upon with the customer
Correct answer: The best short-term capability the process has demonstrated under ideal conditions
Process entitlement is the best capability the process has ever achieved over a short period, representing its potential performance under ideal conditions.
Question 6: During a process audit 6 months after project closure, the Green Belt finds operators are not following the new SOP. The FIRST action should be:
- Report the issue to senior leadership immediately
- Understand WHY operators deviate before implementing additional controls (Correct answer)
- Revert to the old process since compliance is too difficult
- Add the deviation to a future DMAIC project scope
Correct answer: Understand WHY operators deviate before implementing additional controls
Understanding the root cause of non-compliance (e.g., unclear steps, tool unavailability, lack of training) is necessary before implementing effective corrective actions.
Question 7: A control chart with very tight control limits relative to specifications suggests:
- The process is barely capable of meeting specifications
- The process is highly capable and the measurement system may be too sensitive (Correct answer)
- The control limits were incorrectly calculated from specification data
- The process requires immediate improvement action
Correct answer: The process is highly capable and the measurement system may be too sensitive
When control limits are much tighter than specification limits, the process Cpk is high, indicating excellent capability with ample room between natural variation and customer tolerances.
Lean Six Sigma Green Belt Certification Control Phase and Sustainment 4
A sustained improvement in a transactional process is BEST evidenced by: