Lean Six Sigma Black Belt Certification Design for Six Sigma (DFSS) 2 — Questions and Answers
Question 1: In Design FMEA (DFMEA), the Risk Priority Number (RPN) is calculated as:
- Severity + Occurrence + Detection
- Severity × Occurrence × Detection (Correct answer)
- Severity × Occurrence / Detection
- Probability of Failure × Cost of Failure
Correct answer: Severity × Occurrence × Detection
RPN = Severity × Occurrence × Detection (each rated 1–10), providing a relative risk score to prioritize which design failure modes require immediate corrective action.
Question 2: A Transfer Function expressed as Y = f(X) in DFSS is used to:
- Transfer lessons learned from one Six Sigma project to the next
- Mathematically describe how input variables influence the critical output response (Correct answer)
- Map the flow of value through a process to identify waste
- Calculate the cost of poor quality attributed to design failures
Correct answer: Mathematically describe how input variables influence the critical output response
The transfer function models the relationship between controllable input variables (Xs) and the critical quality output (Y), enabling designers to predict and optimize performance before physical prototypes are built.
Question 3: Monte Carlo simulation is used in DFSS primarily to:
- Generate random test scenarios to validate software functionality
- Propagate input variation through a design model to predict the output distribution (Correct answer)
- Create randomized experiment designs for a DOE study
- Randomly sample production lots for outgoing quality inspection
Correct answer: Propagate input variation through a design model to predict the output distribution
Monte Carlo simulation runs thousands of randomized trials using probability distributions for input variables to predict how variation in those inputs will affect the critical output, revealing design risk before prototyping.
Question 4: Tolerance design in DFSS is best described as:
- Determining the acceptable variation ranges for key design parameters to keep CTQ outputs within specification (Correct answer)
- Setting acceptable defect levels for final inspection of finished goods
- Designing products to be tolerant of customer misuse or abuse
- Establishing time limits for completing each phase of the DFSS roadmap
Correct answer: Determining the acceptable variation ranges for key design parameters to keep CTQ outputs within specification
Tolerance design determines how much variation is allowable in each design input parameter so that the critical output (CTQ) remains within its specification limits, balancing quality performance against manufacturing cost.
Question 5: Which DFSS reliability tool uses a top-down, deductive approach to identify combinations of component failures that can cause a system-level failure?
- Control Chart
- Fault Tree Analysis (FTA) (Correct answer)
- Process Capability Study
- Value Stream Map
Correct answer: Fault Tree Analysis (FTA)
Fault Tree Analysis (FTA) starts with an undesired top-level system failure and works downward through logical gates to identify combinations of component-level failures and events that could cause it.
Question 6: In the DMADV roadmap, the Verify phase primarily involves:
- Verifying that root causes of defects have been correctly identified in the Analyze phase
- Piloting the design, validating performance against CTQs, and transitioning to full-scale production (Correct answer)
- Verifying that the project charter is aligned with the company's strategic objectives
- Conducting hypothesis tests on historical data to confirm baseline performance
Correct answer: Piloting the design, validating performance against CTQs, and transitioning to full-scale production
The Verify phase confirms the new design meets all CTQ requirements through prototype testing or pilot production, then ensures a smooth handoff to the process owner for sustained operation.
Question 7: Robust design, based on Taguchi methods, aims to achieve which of the following?
- Ensure all design specifications are met under ideal laboratory conditions only
- Make product or process performance insensitive to uncontrollable noise factors and variation (Correct answer)
- Reduce the number of design iterations required before product launch
- Eliminate all sources of defects through comprehensive 100% final inspection
Correct answer: Make product or process performance insensitive to uncontrollable noise factors and variation
Robust design optimizes design parameter settings so that CTQ performance remains consistent despite uncontrollable noise factors such as environmental variation, manufacturing variation, and product wear.
Lean Six Sigma Black Belt Certification Design for Six Sigma (DFSS) 2
In Design FMEA (DFMEA), the Risk Priority Number (RPN) is calculated as: