Lean Six Sigma Yellow Belt Certification Prep 4 — Questions and Answers
Question 1: A team creates a fishbone (Ishikawa) diagram. Which of the following is NOT a standard category of causes used in manufacturing?
- Customers (Correct answer)
- Machines
- Methods
- Measurement
Correct answer: Customers
The standard 6M fishbone categories in manufacturing are: Man, Machine, Method, Material, Measurement, and Mother Nature (Environment) — not Customers.
Question 2: What does a control chart's Upper Control Limit (UCL) represent?
- Three standard deviations above the process mean, indicating common cause variation boundaries (Correct answer)
- The maximum specification limit set by the customer
- The highest acceptable defect count
- The goal the process should aim to exceed
Correct answer: Three standard deviations above the process mean, indicating common cause variation boundaries
UCL is calculated as the mean plus 3 sigma (3 standard deviations) and represents the upper boundary of expected natural process variation.
Question 3: Which DMAIC phase focuses on identifying the root cause of the problem?
- Analyze (Correct answer)
- Measure
- Improve
- Control
Correct answer: Analyze
The Analyze phase uses statistical and graphical tools to identify and verify the root causes driving the problem identified in Define and quantified in Measure.
Question 4: A team plots cycle time vs. batch size and finds a strong positive correlation. This analysis is best visualized using a:
- Scatter diagram (Correct answer)
- Run chart
- Box plot
- Pareto chart
Correct answer: Scatter diagram
A scatter diagram plots two variables against each other to visually reveal whether and how strongly they are correlated.
Question 5: In Lean, 'takt time' represents:
- The rate at which customers demand products, calculated as available time divided by customer demand (Correct answer)
- The time it takes to complete one unit from start to finish
- The time a machine is idle between jobs
- The maximum allowable defect time per shift
Correct answer: The rate at which customers demand products, calculated as available time divided by customer demand
Takt time = Available Production Time / Customer Demand; it sets the production rhythm needed to meet customer demand without overproducing.
Question 6: A Yellow Belt should primarily support which of the following on a Six Sigma project?
- Data collection, local process knowledge, and implementing improvements in their work area (Correct answer)
- Leading the full DMAIC project independently
- Approving the project charter and budget
- Training Black Belts and Green Belts
Correct answer: Data collection, local process knowledge, and implementing improvements in their work area
Yellow Belts are frontline contributors who provide process expertise, assist with data collection, and help implement solutions designed by higher belts.
Question 7: Which statement best describes the difference between 'special cause' and 'common cause' variation?
- Special cause variation is unpredictable and from specific identifiable sources; common cause is inherent, random variation in the system (Correct answer)
- Common cause variation is from machine breakdowns; special cause is from normal process noise
- Special cause variation is always worse than common cause variation
- Common cause variation must be eliminated first before addressing special causes
Correct answer: Special cause variation is unpredictable and from specific identifiable sources; common cause is inherent, random variation in the system
Special cause variation is unusual, identifiable, and must be eliminated; common cause variation is natural system noise that requires process redesign to reduce.
Lean Six Sigma Yellow Belt Certification Prep 4
A team creates a fishbone (Ishikawa) diagram.
Which of the following is NOT a standard category of causes used in manufacturing?