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Free CRE Practice Questions

10 free, exam-style Certified Reliability Engineer (CRE) practice questions with answers and explanations. No signup required. Work through them below, then take the full free CRE practice test to study every exam domain.

Question 1

A repairable system has MTBF = 800 hours and MTTR = 8 hours. The inherent availability (Ai) is:

  1. 0.90
  2. 0.95
  3. 0.99
  4. 0.999
Show answer & explanation

Correct answer: C - 0.99

Question 2

A system has an MTBF of 2,000 hours (exponential distribution). The reliability at t = 500 hours is approximately:

  1. 0.25
  2. 0.779
  3. 0.607
  4. 0.368
Show answer & explanation

Correct answer: B - 0.779

Question 3

A Weibull analysis yields β = 0.7 and η = 5,000 hours. This indicates:

  1. Constant failure rate (useful life region)
  2. Decreasing failure rate (infant mortality region)
  3. Increasing failure rate (wearout region)
  4. Normal distribution approximation
Show answer & explanation

Correct answer: B - Decreasing failure rate (infant mortality region)

Question 4

An engineer uses the 5 Whys technique and concludes that the root cause is 'operator error.' The PRIMARY problem with this conclusion is:

  1. Operator error is never a contributing factor
  2. The investigation stopped too soon - 'operator error' is typically a symptom, not a root cause
  3. The 5 Whys technique cannot identify systemic issues behind human errors
  4. Operator errors should never be documented as findings
Show answer & explanation

Correct answer: B - The investigation stopped too soon - 'operator error' is typically a symptom, not a root cause

Question 5

An FMEA team assigns Severity = 10, Occurrence = 2, Detection = 3. The RPN is 60. Another failure mode has S = 5, O = 6, D = 4 with RPN = 120. Which should be prioritized?

  1. The failure mode with RPN = 120 because the RPN is higher
  2. The failure mode with Severity = 10 because safety-critical severity takes priority
  3. Both should be prioritized equally since both have significant risks
  4. Neither requires immediate action because both RPNs are manageable
Show answer & explanation

Correct answer: B - The failure mode with Severity = 10 because safety-critical severity takes priority

Question 6

Events A (P = 0.03) and B (P = 0.05) are connected to the top event through an OR gate. The probability of the top event is:

  1. 0.08
  2. 0.0015
  3. 0.0785
  4. 0.9215
Show answer & explanation

Correct answer: C - 0.0785

Question 7

A component is tested at 125°C (398K) with a use temperature of 55°C (328K) and activation energy Ea = 0.7 eV. Using the Arrhenius model (k = 8.617 × 10⁻⁵ eV/K), the acceleration factor is approximately:

  1. AF ≈ 77
  2. AF ≈ 10
  3. AF ≈ 2.3
  4. AF ≈ 500
Show answer & explanation

Correct answer: A - AF ≈ 77

Question 8

A 2-out-of-3 system with identical components (R = 0.90) has system reliability:

  1. Rs = 3(0.90)²(0.10) + (0.90)³ = 0.972
  2. Rs = (0.90)³ = 0.729
  3. Rs = 1 − (0.10)³ = 0.999
  4. Rs = 3 × 0.90 = 2.70
Show answer & explanation

Correct answer: A - Rs = 3(0.90)²(0.10) + (0.90)³ = 0.972

Question 9

A system has two LRUs: LRU-A (λ = 0.002/hr, MTTR = 2 hr) and LRU-B (λ = 0.005/hr, MTTR = 4 hr). The system MTTR is:

  1. 3.43 hours
  2. 3.0 hours
  3. 4.0 hours
  4. 2.5 hours
Show answer & explanation

Correct answer: A - 3.43 hours

Question 10

Preventive maintenance is NOT effective when the component has:

  1. An increasing failure rate
  2. A constant failure rate (β = 1, exponential)
  3. A Weibull β > 2
  4. A decreasing failure rate over time
Show answer & explanation

Correct answer: B - A constant failure rate (β = 1, exponential)

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