tow stage design for estimating the reliability of series/parallel systems

this work aims to determine in a practical and straightforward manner an efficient sampling scheme for estimating the reliability of series/parallel systems. one of the most crucial tasks is to determine the optimal number of units to sample. the sampling schemes given by the authors are complex and costly. we give a reliability sequential scheme which performs much better than the balanced allocation. for a large total number of units, the first order asymptotic optimality of such a scheme is validated by monte carlo simulations.