A Comparison of the Bad as Old and Superimposed Renewal Models

For the bad as old (BAO) model for system reliability, asymptotic distributions for time between failures and time of rth failure are obtained. For series systems, inequalities are obtained for the BAO and superimposed renewal (SR) models for distributions of number of failures and time between failures. Approximations for the distribution of number of failures are obtained for the BAO model for new, large series systems. Consideration is given to the use of BAO probabilities as approximations to SR probabilities for series systems.