A measure, h(t), of the chance that a component, still working at age t, is about to fail. Formally, it is defined by The hazard rate is related to the probability density function, f, and the survivor function,S, by the equation
f(t)= h (t) S(t).
For many situations the graph of a hazard rate is a bathtub curve (see diagram opposite): initially the rate is high as the component beds in, there is then a constant hazard rate, and finally the component starts to wear out.
Hazard rate. The typical bathtub curve that results from a plot of the hazard rate against time. A high initial rate falls to a ‘normal level’ and then slowly increases as ageing sets in.
Subjects: Probability and Statistics.