RESIDUAL LIFETIME DISTRIBUTION AND ITS APPLICATIONS

Let T be a continuous positive random variable representing the lifeti me of an entity. This entity could be a human being, an animal or a pl ant, or a component of a mechanical or electrical system. For nonlivin g objects the lifetime is defined as the total amount of time for whic h the entity carries out its function satisfactorily. The concept of a ging involves the adverse effects of age such as increased probability of failure due to wear. In this paper, we consider certain characteri stics of the residual lifetime distribution at age t, such as the mean , median, and variance, as describing aging. Gamma and Weibull familie s of distributions are studied from this point of view. Explicit asymp totic expressions for the mean, variance and the percentiles of corres ponding residual lifetime distributions are found. Finally these famil ies of distributions are fitted to four sets of actual data, two of wh ich are entirely new. The results can be used in discriminating differ ent shape parameters.