Practice Test Geeks(CRE) Certified Reliability Engineer Practice Test
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Reliability Fundamentals Flashcards

7 cards from real CRE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Reliability Fundamentals flashcards as text

  1. A product reliability specification states '90% reliability at 1000 hours with 90% confidence.' What does this specification require?

    Answer: At least 90% of units survive 1000 hours, demonstrated with 90% statistical confidence

    This R90C90 specification requires that the true population reliability at 1000 hours is at least 90%, demonstrated with 90% confidence from test data.

  2. Which of the following statements about preventive maintenance (PM) is correct for a component with a Weibull β > 1?

    Answer: PM can improve reliability because the component wears out and benefits from periodic replacement

    When β > 1, the hazard rate increases with age (wear-out), so periodic preventive replacement before end-of-life improves system reliability.

  3. What is the failure rate of a series system composed of three components with failure rates λ₁ = 0.001, λ₂ = 0.002, and λ₃ = 0.003 (all per hour)?

    Answer: 0.006 per hour

    For a series system with constant failure rates, the system failure rate is the sum: λ_sys = 0.001 + 0.002 + 0.003 = 0.006/hr.

  4. Which of the following is the most accurate definition of 'mission reliability'?

    Answer: The probability that a system completes a specific mission without failure for a defined duration

    Mission reliability is the probability of completing a defined mission (specific duration and conditions) without failure.

  5. What distinguishes a homogeneous Poisson process (HPP) from a non-homogeneous Poisson process (NHPP) in repairable system analysis?

    Answer: HPP has a constant failure intensity; NHPP has a time-varying failure intensity

    HPP assumes a constant rate of occurrence of failures (ROCOF), while NHPP allows the ROCOF to change over time, capturing trends like reliability growth or degradation.

  6. A reliability engineer calculates a 60% lower confidence bound on MTBF from test data. What does this bound mean?

    Answer: There is 60% confidence that the true MTBF is at least this value

    A one-sided lower 60% confidence bound means there is 60% confidence (based on the test data) that the true MTBF is at or above the stated value.

  7. In reliability engineering, what is the purpose of a 'burn-in' process?

    Answer: To screen out early-life failures (infant mortality) before delivering products to customers

    Burn-in operates products under stress to trigger and remove infant mortality failures before field deployment, improving initial field reliability.