On the Software Reliability Models of Jelinski-Moranda and Littlewood

This note provides an alternative formulation of the software reliability models of Jelinski-Moranda and Littlewood. The formulation is in terms of failure times rather than interfailure times; the models are then equivalent to observing the first n order statistics (n is random) from a random sample of size N. The models can be generalized by using a decreasing failure rate for the failure times. For the Jelinski-Moranda model, we comment on the maximum likelihood estimate and an improved estimate for the initial number of faults in the software. We discuss how to check the validity of the Jelinski-Moranda model.