Technical Note—Fault Testing for a k-out-of-n System

Butterworth [Opns. Res. 20, 335–343 (1972)] has presented a sufficient condition for the optimality of a sequential testing procedure for k-out-of-n systems. The condition is fairly strong and therefore excludes several cases where in fact an optimal policy exists. This note presents an optimal sequential procedure for the k-out-of-n system with equal testing costs for all components, a case where Butterworth's sufficient condition is not satisfied.