Lean Six Sigma Green Belt Certification Improve Phase and Solutions 4 — Questions and Answers
Question 1: What does 'takt time' represent in a lean production environment?
- The time required to complete one unit at full machine speed
- The available production time divided by customer demand rate (Correct answer)
- The total lead time from order to delivery
- The time lost due to unplanned downtime
Correct answer: The available production time divided by customer demand rate
Takt time = available production time ÷ customer demand rate, setting the rhythm at which products must be completed to meet demand.
Question 2: In a DOE, a 'main effect' refers to:
- The combined effect of two factors acting together
- The average change in the response caused by changing one factor from low to high (Correct answer)
- The unexplained variation in the experimental results
- The interaction between all factors simultaneously
Correct answer: The average change in the response caused by changing one factor from low to high
A main effect is the average change in the response variable when a single factor moves from its low level to its high level, averaged across all levels of other factors.
Question 3: Which lean concept describes the continuous flow of a single unit through a process without batching?
- Push production
- One-piece flow (Correct answer)
- Batch and queue
- Economic order quantity
Correct answer: One-piece flow
One-piece flow moves individual units through each process step immediately, eliminating batching and reducing WIP and lead time.
Question 4: A team is choosing between two solutions. Solution A has a high impact but high risk; Solution B has moderate impact and low risk. Which tool helps formally evaluate this trade-off?
- Pareto chart
- Risk-benefit matrix (Correct answer)
- Histogram
- Run chart
Correct answer: Risk-benefit matrix
A risk-benefit (or impact-effort) matrix plots solutions by their risk/cost versus their expected benefit to support structured decision-making.
Question 5: In a simulation model used for process improvement, 'Monte Carlo simulation' is useful for:
- Designing controlled experiments with physical machines
- Estimating the distribution of outcomes by randomly sampling input variables (Correct answer)
- Calculating the exact optimal process setting
- Eliminating all variation from the process
Correct answer: Estimating the distribution of outcomes by randomly sampling input variables
Monte Carlo simulation repeatedly samples from input probability distributions to generate a distribution of possible output values, modeling process uncertainty.
Question 6: Which type of kanban signals that a work center needs more materials from an upstream supplier or process?
- Production kanban
- Withdrawal (move) kanban (Correct answer)
- Emergency kanban
- Signal kanban
Correct answer: Withdrawal (move) kanban
A withdrawal (or move) kanban authorizes the movement of a specific quantity of material from an upstream store to a downstream process.
Question 7: After implementing a process change, a team runs a two-sample t-test and obtains a p-value of 0.03. At α = 0.05, what should they conclude?
- Fail to reject the null hypothesis; no significant difference
- Reject the null hypothesis; there is a statistically significant difference (Correct answer)
- The sample size was too small to draw conclusions
- The process change had no practical significance
Correct answer: Reject the null hypothesis; there is a statistically significant difference
Since p-value (0.03) < α (0.05), the team rejects the null hypothesis, concluding there is a statistically significant difference between before and after.
Lean Six Sigma Green Belt Certification Improve Phase and Solutions 4
What does 'takt time' represent in a lean production environment?