System availability analysis with two failure modes of random failure and wear-out failure

Recently, Cao et al. considered the mean availability of a system that has multiple failure modes. Thus led to the creation of a formula for the mean availability of systems with multiple failure modes (i.e., random and wear-out failure modes). The formula of the mean availability derived by Cao et al. requires an exact distribution function of failure-time distribution that wear-out failures follow. However, there are often cases where information such as average and standard deviation are only known, and the exact distribution function isn't specified. In this article, under limited information such as average and standard deviation about wear-out failure mode, we address a procedure for evaluating the mean availability of a system that has random failure and wear-out failure modes.