CRE CRE Statistical Methods and Reliability Modeling 2 — Questions and Answers
Question 1: Accelerated Life Testing (ALT) uses elevated stress levels primarily to accomplish which goal?
- Intentionally destroy components for disposal
- Reduce test time by inducing failures faster than normal operating conditions (Correct answer)
- Validate compliance with safety regulations
- Measure components under standard operating conditions
Correct answer: Reduce test time by inducing failures faster than normal operating conditions
ALT compresses the failure timeline so reliability predictions can be made without waiting for failures under normal conditions.
Question 2: The Arrhenius model in reliability testing is used to describe the effect of which stress variable on failure rates?
- Vibration amplitude
- Temperature (Correct answer)
- Humidity level
- Supply voltage
Correct answer: Temperature
The Arrhenius model relates reaction rate (failure rate) to temperature using the activation energy equation.
Question 3: For two components in parallel with reliabilities R1 and R2, the combined system reliability is calculated as:
- R1 × R2
- 1 − (1 − R1)(1 − R2) (Correct answer)
- R1 + R2
- min(R1, R2)
Correct answer: 1 − (1 − R1)(1 − R2)
Parallel system reliability = 1 minus the probability that both components fail simultaneously.
Question 4: In reliability testing, confidence intervals are used to:
- Increase the required sample size
- Quantify uncertainty in reliability point estimates (Correct answer)
- Remove statistical outliers from test data
- Calibrate test measurement equipment
Correct answer: Quantify uncertainty in reliability point estimates
Confidence intervals provide a range within which the true reliability parameter is expected to fall with a stated probability.
Question 5: The inverse power law model is commonly applied in accelerated life testing for which type of stress?
- Thermal (temperature) stress
- Voltage or mechanical stress (Correct answer)
- Thermal cycling
- Corrosive humidity
Correct answer: Voltage or mechanical stress
The inverse power law relates failure rate to non-thermal stresses such as voltage, pressure, or vibration.
Question 6: Monte Carlo simulation in reliability analysis is primarily used to:
- Generate simulated failure times mathematically from probability distributions (Correct answer)
- Test physical hardware prototypes under stress
- Calibrate precision measurement instruments
- Document failure modes for FMEA tables
Correct answer: Generate simulated failure times mathematically from probability distributions
Monte Carlo simulation randomly samples input distributions to model system behavior and estimate reliability metrics.
CRE CRE Statistical Methods and Reliability Modeling 2
Accelerated Life Testing (ALT) uses elevated stress levels primarily to accomplish which goal?