Description:
<jats:p>This paper considers a problem of determining the optimal number of units for a parallel redundant system. The optimal number <jats:italic>N∗</jats:italic> to minimize the expected cost is given by a unique solution of equations. When the system is replaced before failure at time <jats:italic>T</jats:italic>, the optimal <jats:italic>N∗</jats:italic> and <jats:italic>T∗</jats:italic> are discussed, and a computing procedure for obtaining these values is specified.</jats:p>