Certified Six Sigma Black Belt Exam Lean Enterprise Concepts 5 — Questions and Answers
Question 1: A value stream map shows a total lead time of 10 days with 45 minutes of value-added time. What is the process cycle efficiency (PCE)?
- 0.31% (Correct answer)
- 4.50%
- 22.2%
- 45.0%
Correct answer: 0.31%
PCE = 45 min ÷ (10 days × 480 min/day) = 45 ÷ 4,800 = 0.9375%, which rounds to approximately 0.31% if using 1440 min/day, confirming very low efficiency typical of batch environments.
Question 2: Which lean concept describes designing and operating a manufacturing cell so that one operator can run multiple machines in sequence, following the parts?
- Line balancing
- Multi-process handling (multi-machine operation) (Correct answer)
- Jidoka cell design
- U-shaped cell takt flow
Correct answer: Multi-process handling (multi-machine operation)
Multi-process handling (multi-machine operation) allows one trained operator to tend multiple machines in sequence, matching output to takt time with fewer people.
Question 3: A lean Black Belt notices that a process produces in large batches and ships weekly, causing large swings in upstream demand. Which lean strategy best addresses this?
- Increase safety stock upstream to buffer against the swings
- Implement heijunka to level production by mix and volume (Correct answer)
- Add a supermarket downstream and use FIFO lanes upstream
- Map the value stream and identify all non-value-added steps
Correct answer: Implement heijunka to level production by mix and volume
Heijunka (production leveling) smooths the production schedule to dampen demand volatility sent to upstream processes, reducing the bullwhip effect.
Question 4: In a lean enterprise, 'little's law' (L = λW) is used to:
- Calculate the number of kanban cards needed in a loop
- Relate average WIP, average throughput rate, and average lead time (Correct answer)
- Determine takt time from customer demand
- Estimate defect rates using statistical sampling
Correct answer: Relate average WIP, average throughput rate, and average lead time
Little's Law states that average WIP (L) equals average arrival rate (λ) multiplied by average time in system (W), connecting inventory, flow rate, and lead time.
Question 5: Which statement best describes the relationship between kaizen and kaikaku in lean transformation?
- Kaizen is radical redesign; kaikaku is incremental improvement
- Kaizen is continuous incremental improvement; kaikaku is radical or breakthrough change (Correct answer)
- Both terms describe the same rapid improvement workshop concept
- Kaikaku applies to processes; kaizen applies only to administrative work
Correct answer: Kaizen is continuous incremental improvement; kaikaku is radical or breakthrough change
Kaizen means continuous incremental improvement by all employees; kaikaku (or kaikaku kaizen) refers to radical, breakthrough redesign of a process or value stream.
Question 6: When applying lean in a transactional (office) environment, which of the following is the lean equivalent of 'inventory' waste?
- Unnecessary meetings and conference calls
- Batches of unprocessed work items such as email queues, approval stacks, or report backlogs (Correct answer)
- Duplicate data entry across multiple software systems
- Walking between offices or floors to obtain information
Correct answer: Batches of unprocessed work items such as email queues, approval stacks, or report backlogs
In transactional processes, WIP inventory manifests as stacks of unprocessed items—emails, forms, approvals—waiting between processing steps.
Question 7: A Black Belt wants to determine the number of kanban cards needed between two processes. Daily demand is 200 units, replenishment lead time is 0.5 days, safety stock factor is 10%, and each container holds 25 units. How many kanban cards are needed?
- 4
- 5 (Correct answer)
- 6
- 8
Correct answer: 5
Kanban cards = [demand × lead time × (1 + safety factor)] ÷ container size = [200 × 0.5 × 1.10] ÷ 25 = 110 ÷ 25 = 4.4, rounded up to 5.
Certified Six Sigma Black Belt Exam Lean Enterprise Concepts 5
A value stream map shows a total lead time of 10 days with 45 minutes of value-added time.
What is the process cycle efficiency (PCE)?