CQE Exam - Question 60

The diagram represents the bathtub curve, a common model for the failure rate of products over time. Period B corresponds to the flat, middle section of the curve, indicating a constant failure rate, which is characteristic of the useful life phase. The reliability function for a constant failure rate is best represented by an exponential decay function: R(t) = e^(-λt), where λ is the constant failure rate. Thus, the correct answer is D.