Lean Six Sigma Green Belt Control Phase and Sustainment 1 Flashcards
6 cards from real Lean Six Sigma Green Belt Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Lean Six Sigma Green Belt Control Phase and Sustainment 1 flashcards as text
In the Control phase, what is the primary function of a control chart's Upper Control Limit (UCL)?
Answer: To signal when a process has shifted beyond natural variation
The UCL (and LCL) on a control chart represent the boundaries of natural process variation (±3 sigma). A data point beyond the UCL signals a special-cause event requiring investigation, not just common-cause noise.
Which of the following best describes a 'mistake-proofing' device implemented during the Control phase?
Answer: A physical or electronic mechanism that prevents a defect from occurring or escaping
Poka-yoke (mistake-proofing) devices are physical or automated mechanisms — like sensors, jigs, or interlocks — that either prevent an error from happening or detect it immediately. They are more robust than procedural controls like checklists.
A Lean Six Sigma team has completed improvements and is closing the project. Which metric best indicates that gains have been sustained six months after handover?
Answer: The process sigma level remaining at or above the improved baseline
Sustained improvement is demonstrated by ongoing process performance data — specifically, the sigma level (or defect rate) remaining at or above the level achieved during the Improve phase, confirming the gains have held.
What is the purpose of a 'lessons learned' document completed at the end of the Control phase?
Answer: To capture knowledge and best practices so future projects can benefit from the team's experience
A lessons learned document captures insights — what worked, what didn't, and what would be done differently — enabling organizational learning and preventing future teams from repeating the same mistakes.
When selecting a control chart type in the Control phase, which chart is appropriate for monitoring the proportion of defective units in a variable-size subgroup?
Answer: p-chart
The p-chart monitors the proportion (fraction) defective and is designed for attribute data where subgroup sizes vary. The c-chart tracks count of defects per unit in fixed-size subgroups, while X-bar/R and I-MR charts are for continuous data.
In the Control phase, what is the recommended response when a single data point falls outside the control limits on an SPC chart?
Answer: Investigate for a special-cause, document findings, and follow the reaction plan
A point outside control limits signals a special-cause variation. The correct response is to investigate the root cause, document what was found, and execute the pre-defined reaction plan — not to recalculate limits or ignore the signal.