Reliability

Which correctly lists the three periods that make up the bathtub curve, showing how failure rate changes over time?

  1. AEarly failure period, random failure period, wear-out failure period
  2. BDesign period, manufacturing period, shipping period
  3. CPrototype period, mass production period, maintenance period
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Answer: A. Early failure period, random failure period, wear-out failure period

The bathtub curve consists of the early failure period, when the failure rate is high at the start of use; the random failure period, when the failure rate is low and nearly constant; and the wear-out failure period, when the failure rate rises due to degradation. Early failures are removed by burn-in and similar screening, and products are designed so wear-out occurs after the product's lifetime.

Bathtub curve (failure rate over time) Time Failure rate Falling Nearly constant Rising Early failures Random failures Wear-out Screened out by burn-in Designed to come after product life
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