Optimal use of partial redundancy and the system reliability which results

Partial system triplication with a single majority vote is analysed to find (a) the region of superiority of partial triplication over total triplication and (b) over no redundancy, (c) the degree of partial triplication which maximises reliability, (d) the maximum system reliability produced by partial redundancy. Only approximate or numerical solutions to (a) and (c) have appeared previously. (b) and (d) are entirely new.