Reliability Applications of a Bivariate Exponential Distribution

Abstract

This paper examines some two-unit systems in which the lifetimes of the two units in service are not independent but depend upon one another in a particular way. This dependence is characterized by the bivariate exponential distribution of Marshall and Olkin, which has exponential marginal distributions and other physically motivating properties. Two measures of reliability are determined: the first is the distribution and mean of the time to system failure (i.e., when all units are failed) and the second gives steady-state probabilities of the number of working units. Some graphical results are given to illustrate the deviation of these quantities from the values obtained under the classical assumption of independent lifetimes.