For a non-repairable component with a constant hazard rate λ, the mean time to failure (MTTF) is equal to which of the following?

• A. λ
• B. e^λ
• C. ln(λ)
• D. 1/λ

Answer: (D)

This question tests understanding that a non-repairable component with a constant hazard rate has an exponential lifetime. A constant hazard rate means the chance of failing in the next instant does not depend on how long the item has already lived, which is the defining property of an exponential distribution with rate λ.

The mean time to failure is the expected lifetime, E[T]. For an exponential distribution with density f(t) = λ e^{-λ t} (t ≥ 0), the expected value is E[T] = ∫0^∞ t λ e^{-λ t} dt = 1/λ. Intuitively, λ is the failure rate per unit time, so its reciprocal gives the average time to failure.

Thus the mean time to failure equals 1/λ.