# TECH SPOT: SAMPLE CRE QUESTIONS (PART 3)

Answers to CRE questions in Sept 2018 Newsletter

Which of the following statements is NOT true?
o Designing for reliability requires risk assessment of the product
o Project schedule should not include tasks for risk assessment
o Cost estimates for reliability testing should be included in the project budget
o Designing for reliability should include user hazard assessment

In which of the following product life cycle phases should product disposal issues be addressed?
o Design/Development
o Concept/Planning
o Operation/Repair
o Wearout/Disposal

During which phase of the product life cycle should testing begin to validate the design?
o Design/Development
o Production/Manufacturing
o Concept/Planning
o Operation/Repair

Which of the following is a metric to describe robust functionality?
o Mean Time To Failure
o Signal to Noise Ratio
o Cost to Value Ratio
o Mean Time To Repair

MTBF and MTTF are two reliability terms that are:
o Synonymous with each other
o Based on the use of the same lifetime distribution
o Are applied differently. MTTF is applicable for maintainable systems. MTBF is only applicable for non‐maintainable / nonrepairable systems
o Are calculated using the second moments of the lifetime distribution.

Which of the following expressions is best used to describe the pattern of failures over time for repairable systems?
o Rate of Occurrence Of Failures
o Hazard rate
o Mean Time To Failure
o Mean Time To Repair

What is the most appropriate definition of Mean Time Between Failures (MTBF)?
o The longest time period that a piece of repairable equipment failed in the record.
o The average time period that a piece of repairable equipment takes to be repaired.
o The average time period that a piece of repairable equipment is operational in the past 6 months.
o The average time period that a piece of repairable equipment is operational.

Which element(s) make a complete reliability goal statement?
o Function, probability, duration and environment.
o Only need MTBF
o Probability, useful life and wear out mechanism
o Function, probability, shipping and environment

The equation, R(t) = e‐λt, is applicable during a product’s:
o infant mortality stage.
o useful life stage.
o wear‐out stage.
o break‐in, useful life stage and wear‐out stages.

Which of the following best describes availability?
o The ability of a product, when used under given conditions, to perform satisfactorily when called upon
o The probability that a product will perform the intended function, in the manner specified, for a particular period of time
o The probability that a failed system can be made operable in a specified interval of downtime
o The degree to which a product is operable and capable of performing its required function at any randomly chosen  time during its specified operating time, provided that the product is available at the start of that period

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