Consider a production system with k machines, where machine i has efficiency vi $>0,$ fori $=1,...,$ k$.$ In each operational cycle, two machines are selected for a performance test,while the other k $2$ machines are queued for the next cycle in an ordered sequence. Themachine that performs less efficiently in the test is placed at the end of the queue, and themore efficient machine is then tested against the next machine in line. When machines i andj are tested, machine i is more efficient with probability vivi$+$vj