Estimation of Reliability Growth in a Complex System with a Poisson-Type Failure

Many modern complex systems, especially those involving numerous electronic components, are subject to failures with operating time that follow a Poisson-type distribution. In the course of development of such a system engineering changes are made, with the object of improving system performance or reliability. As a result, no two successive assemblies are alike in all components, although only a few changes may have been made across assemblies. It is nevertheless desirable to know at the earliest possible time in the development program 1 the level of reliability of the system, 2 whether reliability is increasing, and if so, how rapidly, and 3 the expected reliability at the end of the projected development program. In this paper, methods are developed for fitting typical reliability growth curves to experimental data by the method of maximum likelihood. Mathematical models are also developed for an idealized engineering development process to provide a basis for the selection of a suitable growth curve.