ASQ Certified Quality Inspector & Reliability Engineer 3 — Questions and Answers
Question 1: Which type of control chart is most appropriate for monitoring the number of defects per unit when the sample size varies?
- np-chart
- p-chart
- u-chart (Correct answer)
- c-chart
Correct answer: u-chart
The u-chart monitors defects per unit and accommodates variable sample sizes, unlike the c-chart which requires constant sample sizes.
Question 2: In reliability engineering, the 'bathtub curve' describes failure rate over time with three distinct phases. Which phase is characterized by a constant failure rate?
- Infant mortality (burn-in) phase
- Useful life phase (Correct answer)
- Wear-out phase
- Overstress phase
Correct answer: Useful life phase
The useful life phase exhibits a constant (random) failure rate, which is modeled by the exponential distribution.
Question 3: A process has a Cp of 1.5 and a Cpk of 0.8. This indicates the process is:
- Capable and centered
- Capable but not centered (Correct answer)
- Not capable but centered
- Neither capable nor centered
Correct answer: Capable but not centered
Cp > 1.33 shows sufficient spread capability, but Cpk < 1.0 indicates the process mean is shifted toward a specification limit.
Question 4: Which gauge R&R outcome indicates that measurement system variation is unacceptably large?
- %GRR below 10%
- %GRR between 10% and 30%
- %GRR above 30% (Correct answer)
- Number of distinct categories above 5
Correct answer: %GRR above 30%
Per AIAG guidelines, a %GRR above 30% indicates the measurement system is unacceptable and needs improvement.
Question 5: In acceptance sampling, the Producer's Risk (α) is the probability of:
- Accepting a lot with quality worse than the LTPD
- Rejecting a lot with quality at or better than the AQL (Correct answer)
- Accepting a defective unit
- Rejecting all units in the lot
Correct answer: Rejecting a lot with quality at or better than the AQL
Producer's Risk (α) is the probability of rejecting a good lot whose quality meets or exceeds the Acceptable Quality Level.
Question 6: A Pareto chart is used in quality inspection primarily to:
- Plot individual measurements over time
- Identify and prioritize the most significant defect categories (Correct answer)
- Determine process capability
- Display the correlation between two variables
Correct answer: Identify and prioritize the most significant defect categories
Pareto charts apply the 80/20 principle to show which defect types account for the largest share of quality problems.
Question 7: For a redundant system where two components each have reliability of 0.90 operate in parallel, what is the system reliability?
- 0.81
- 0.90
- 0.99 (Correct answer)
- 1.00
Correct answer: 0.99
Parallel system reliability = 1 − (1−0.90)(1−0.90) = 1 − 0.01 = 0.99.
ASQ Certified Quality Inspector & Reliability Engineer 3
Which type of control chart is most appropriate for monitoring the number of defects per unit when the sample size varies?