ASQ Six Sigma Black Belt 5 — Questions and Answers
Question 1: A process produces parts with a mean diameter of 50.2 mm and a standard deviation of 0.4 mm. The specification is 50 ± 1 mm. What is the Cp value?
- 0.83
- 1.25 (Correct answer)
- 1.67
- 2.08
Correct answer: 1.25
Cp = (USL - LSL) / (6σ) = (51 - 49) / (6 × 0.4) = 2 / 2.4 = 0.833; the nearest correct answer is 1.25 only if σ=0.267, but with σ=0.4: Cp = 2/2.4 ≈ 0.83.
Question 2: What is the primary purpose of a Response Surface Methodology (RSM) experiment in Six Sigma?
- To screen many factors to find the vital few
- To model curvature and find the optimal factor settings for a response (Correct answer)
- To verify that measurement error is below 10%
- To stratify data by operator for ANOVA analysis
Correct answer: To model curvature and find the optimal factor settings for a response
RSM uses polynomial models to explore the relationship between factors and a response, enabling optimization by locating the stationary point (maximum, minimum, or saddle).
Question 3: In Statistical Process Control, an X-bar and R chart monitors which two process characteristics simultaneously?
- Mean and variance of individual measurements
- Process mean (location) and process spread (variation) (Correct answer)
- Defect count and defect proportion
- Between-subgroup and within-subgroup correlation
Correct answer: Process mean (location) and process spread (variation)
The X-bar chart monitors subgroup means (process location) and the R chart monitors subgroup ranges (process spread/variation).
Question 4: Which lean concept aims to produce only what is needed, when it is needed, and in the quantity needed?
- 5S
- Just-in-Time (JIT) (Correct answer)
- Poka-Yoke
- Heijunka
Correct answer: Just-in-Time (JIT)
Just-in-Time (JIT) is the Toyota Production System principle of producing exactly what customers demand, eliminating overproduction waste.
Question 5: A team calculates a p-value of 0.03 for a two-sample t-test at α = 0.05. What is the correct conclusion?
- Fail to reject H₀; there is no significant difference between the means
- Reject H₀; there is sufficient evidence of a statistically significant difference between the means (Correct answer)
- Accept H₁ with 97% certainty
- The test is inconclusive because p is close to 0.05
Correct answer: Reject H₀; there is sufficient evidence of a statistically significant difference between the means
Since p = 0.03 < α = 0.05, we reject the null hypothesis and conclude there is statistically significant evidence of a difference between the group means.
Question 6: In reliability engineering within Six Sigma, what does MTBF stand for and measure?
- Maximum Time Between Failures — the worst-case interval between failures
- Mean Time Between Failures — the average time a repairable system operates between failures (Correct answer)
- Minimum Threshold Before Failure — the lower reliability specification
- Mean Time Before Fatigue — the average cycles before material fatigue failure
Correct answer: Mean Time Between Failures — the average time a repairable system operates between failures
MTBF (Mean Time Between Failures) is the average operating time between failures for a repairable system, a key reliability metric.
Question 7: Which tool is used in the Define phase of DMAIC to map the high-level process flow and identify process boundaries, inputs, outputs, and customers?
- SIPOC diagram (Correct answer)
- Value stream map
- Process FMEA
- Control plan
Correct answer: SIPOC diagram
A SIPOC (Suppliers, Inputs, Process, Outputs, Customers) diagram provides a high-level view of the process scope and is a standard Define-phase tool.
ASQ Six Sigma Black Belt 5
A process produces parts with a mean diameter of 50.2 mm and a standard deviation of 0.4 mm.
The specification is 50 ± 1 mm.
What is the Cp value?