Simple plots for monitoring the field reliability of repairable systems

This paper illustrates a few simple plots that aid in tracking the field reliability of a group of systems. Reliability practitioners often attempt to model repairable systems with sophisticated statistical methods such as non-homogeneous Poisson processes (NHPP) and maximum likelihood parameter estimation. Reliability is ascertained as a function of time without resorting to complex stochastic techniques and while maintaining statistical rigor. Analyses based on the mean cumulative function (MCF) are simple and easily understandable by decision makers.