Lean Six Sigma Yellow Belt Certification Lean Six Sigma Yellow Belt The Control Phase 1 — Questions and Answers
Question 1: In the Control phase, what is the primary purpose of a reaction plan?
- To outline steps the team takes when a process metric goes out of control (Correct answer)
- To document the root causes identified during the Analyze phase
- To assign financial accountability for project outcomes
- To schedule future improvement projects for the same process
Correct answer: To outline steps the team takes when a process metric goes out of control
A reaction plan specifies the predefined steps operators and supervisors must follow when a control chart signals an out-of-control condition, ensuring the process is corrected quickly and consistently without waiting for further analysis.
Question 2: Which of the following BEST describes mistake-proofing (Poka-Yoke) as a Control phase strategy?
- Using statistical software to predict future defects
- Designing the process so errors are physically impossible or immediately detected (Correct answer)
- Retraining operators on existing procedures every quarter
- Increasing inspection frequency at the end of the production line
Correct answer: Designing the process so errors are physically impossible or immediately detected
Poka-Yoke devices or design changes make it impossible or very difficult for a defect to occur or escape detection, which is a highly robust control method that does not rely on operator vigilance or periodic audits.
Question 3: A process capability index (Cpk) of 1.33 monitored during the Control phase generally indicates that the process is:
- Barely meeting specification limits with little room for variation
- Capable and meeting specifications with a reasonable safety margin (Correct answer)
- Highly optimized and essentially defect-free at Six Sigma performance
- Out of control and requiring immediate corrective action
Correct answer: Capable and meeting specifications with a reasonable safety margin
A Cpk of 1.33 corresponds to roughly a 4-sigma process, meaning the process is producing output well within specification limits with an adequate buffer — it is considered capable but not yet at Six Sigma (Cpk ≈ 2.0) performance.
Question 4: What is the main purpose of conducting periodic process audits during the Control phase?
- To identify new improvement opportunities for a follow-on DMAIC project
- To verify that operators and the process continue to follow the improved standard work (Correct answer)
- To recalculate the financial savings originally projected at project launch
- To present findings to senior leadership for budget approval
Correct answer: To verify that operators and the process continue to follow the improved standard work
Periodic audits confirm that the gains achieved during the Improve phase have been sustained — that operators are following updated procedures and the process has not reverted to old habits over time.
Question 5: Which control chart would be MOST appropriate for tracking the number of defects per unit when the subgroup size changes from sample to sample?
- X-bar and R chart
- p-chart
- u-chart (Correct answer)
- c-chart
Correct answer: u-chart
The u-chart (defects per unit) is designed for situations where defect counts are tracked and the sample size varies between subgroups. The c-chart also tracks defect counts but assumes a constant sample size, making the u-chart the correct choice here.
Question 6: At the close of the Control phase, a 'lessons learned' document is PRIMARILY intended to:
- Formally assign blame for problems encountered during the project
- Capture knowledge and insights so future project teams can avoid similar pitfalls and replicate successes (Correct answer)
- Replace the control plan as the primary reference for the process owner
- Justify additional headcount resources for ongoing monitoring
Correct answer: Capture knowledge and insights so future project teams can avoid similar pitfalls and replicate successes
A lessons learned document preserves the team's practical experience — what worked, what didn't, and what they would do differently — making this knowledge available to future improvement teams across the organization rather than letting it disappear when the team disbands.
Lean Six Sigma Yellow Belt Certification Lean Six Sigma Yellow Belt The Control Phase 1
In the Control phase, what is the primary purpose of a reaction plan?