Lean Six Sigma Black Belt Certification Assessment 3 — Questions and Answers
Question 1: A Black Belt wants to assess whether a process is in statistical control before calculating capability indices. Which tool is most appropriate?
- Control chart (Correct answer)
- Histogram
- Pareto chart
- Scatter diagram
Correct answer: Control chart
Capability indices are only meaningful when the process is stable; a control chart must confirm the absence of special-cause variation before computing Cp or Cpk.
Question 2: Which formula correctly defines process sigma level from defects per million opportunities (DPMO)?
- Sigma = NORMSINV(1 - DPMO/1,000,000) + 1.5 (Correct answer)
- Sigma = DPMO / 3.4
- Sigma = 1,000,000 / DPMO × 6
- Sigma = NORMSINV(DPMO/1,000,000) - 1.5
Correct answer: Sigma = NORMSINV(1 - DPMO/1,000,000) + 1.5
Process sigma is calculated by converting DPMO to a Z-value using the inverse normal CDF and adding the 1.5 sigma long-term shift adjustment.
Question 3: During baselining, a Black Belt calculates a rolled throughput yield (RTY) of 0.62 across four process steps. What does this mean?
- 62% of units complete all four steps without any defect (Correct answer)
- The first-pass yield at each step averages 62%
- 38% of units are scrapped before reaching the last step
- The process produces 62 defects per 100 units
Correct answer: 62% of units complete all four steps without any defect
RTY is the probability that a unit passes through all process steps without requiring rework or being defective; 0.62 means 62% of units are defect-free throughout.
Question 4: Which assessment tool maps the current state of a process by depicting all activities, delays, and information flows to identify waste?
- Value Stream Map (Correct answer)
- SIPOC diagram
- Affinity diagram
- Cause-and-effect matrix
Correct answer: Value Stream Map
A Value Stream Map (VSM) visualizes material and information flows with cycle times, wait times, and inventory counts, making waste visible for elimination.
Question 5: A measurement system shows acceptable Gage R&R %Study Variation but fails the bias test. What is the best corrective action?
- Calibrate or adjust the measurement instrument (Correct answer)
- Increase the number of operators in the study
- Accept the system since repeatability is good
- Switch to an attribute measurement system
Correct answer: Calibrate or adjust the measurement instrument
Bias (systematic error) indicates the measurement system consistently reads high or low relative to the true value, which is corrected by calibration or instrument adjustment.
Question 6: In FMEA conducted during process assessment, the Risk Priority Number (RPN) is calculated as:
- Severity × Occurrence × Detection (Correct answer)
- Severity + Occurrence + Detection
- Severity × Occurrence / Detection
- Severity × Detection / Occurrence
Correct answer: Severity × Occurrence × Detection
RPN = Severity × Occurrence × Detection, providing a composite risk score used to prioritize failure modes for corrective action.
Question 7: When assessing process data, a Black Belt finds data is right-skewed and uses Ppk instead of Cpk. What is the key difference between these indices?
- Ppk uses overall (long-term) standard deviation; Cpk uses within-subgroup (short-term) standard deviation (Correct answer)
- Ppk is used for attribute data; Cpk is used for variable data
- Ppk requires a normal distribution; Cpk does not
- Ppk measures accuracy; Cpk measures precision
Correct answer: Ppk uses overall (long-term) standard deviation; Cpk uses within-subgroup (short-term) standard deviation
Ppk uses the overall sample standard deviation capturing all sources of variation, while Cpk uses the within-subgroup standard deviation reflecting only short-term variation.
Lean Six Sigma Black Belt Certification Assessment 3
A Black Belt wants to assess whether a process is in statistical control before calculating capability indices.
Which tool is most appropriate?