Steps & Spikes

To paraphrase a quotation from the ‘Reliability Edge’ web site, "The concept of flat earth is not now widely defended, but the unsupported assumption that most reliability engineering problems can be modeled well by the exponential distribution is still widely held. In a quest for simplicity and solutions that we can grasp, derive and easily communicate, many practitioners have embraced simple equations derived from the underlying assumption of an exponential distribution for reliability prediction, accelerated testing, reliability growth, maintainability and system reliability analyses. This practice is perpetuated by some reliability authors and lecturers, some reliability software makers, and most military standards that deal with reliability".

Our experiences with the effect of these assumptions being alternately over-simplify, and then complicate, with "Polynomial Contrasts", Latin Squares and Weibull Analyses result in the bathtub curve being transformed into a powerful source of misinformation.