Statistical Preliminaries

The probabilistic nature of system reliability arises from the fact that the performance parameter (which is a random variable) of the system follows a pattern, which may be expressed in probabilistic terms. The function, which describes this pattern or distribution of the performance parameter of a system, is known as the distribution function.

If the particular set of performance (or failure) are well represented by a particular distribution it can be concluded that the failure characteristic follow that particular distribution.