Reliability Data Analysis and Statistics Flashcards

What does MTBF stand for in reliability engineering?

Answer: Mean Time Between Failures

MTBF (Mean Time Between Failures) is the average time between successive failures of a repairable system and is a foundational reliability metric.

Which formula correctly calculates failure rate (λ) from MTBF?

Answer: λ = 1 / MTBF

Failure rate (λ) equals 1/MTBF, representing the frequency of failures per unit of operating time.

What does the bathtub curve illustrate in reliability engineering?

Answer: The failure rate pattern showing infant mortality, constant rate, and wear-out phases

The bathtub curve describes the three phases of equipment life: infant mortality (decreasing failure rate), useful life (constant rate), and wear-out (increasing failure rate).

What is 'censored data' in the context of reliability analysis?

Answer: Data from units that have not failed or were removed before failure

Censored (suspended) data represents units that have not yet failed or were removed from service before failure, requiring special statistical methods for inclusion in reliability calculations.

If a pump has an MTBF of 2,000 hours and an MTTR of 8 hours, what is its inherent availability?

Answer: 99.6%

Availability = MTBF / (MTBF + MTTR) = 2000 / (2000 + 8) = 2000 / 2008 ≈ 0.996 or 99.6%.

Reliability is formally defined as the probability that a system performs its required function for a specified period under which conditions?

Answer: Under stated conditions for a specified time interval

Reliability is the probability that an item performs its required function under given (stated) conditions for a specified time interval, per IEEE and IEC standards.

For a component following the exponential distribution with an MTBF of 500 hours, what is its reliability at t = 500 hours?

Answer: 36.8%

For exponential distribution, R(t) = e^(-t/MTBF); at t = MTBF, R = e^(-1) ≈ 0.368 or 36.8%.