Published online by Cambridge University Press: 14 July 2016
Let γ t  and δ t  denote the residual life at t and current life at t, respectively, of a renewal process  , with
, with  the sequence of interarrival times. We prove that, given a function G, under mild conditions, as long as
 the sequence of interarrival times. We prove that, given a function G, under mild conditions, as long as  holds for a single positive integer n, then
 holds for a single positive integer n, then  is a Poisson process. On the other hand, for a delayed renewal process
 is a Poisson process. On the other hand, for a delayed renewal process  with
 with  the residual life at t, we find that for some fixed positive integer n, if
 the residual life at t, we find that for some fixed positive integer n, if  is independent of t, then
 is independent of t, then  is an arbitrarily delayed Poisson process. We also give some corresponding results about characterizing the common distribution function F of the interarrival times to be geometric when F is discrete. Finally, we obtain some characterization results based on the total life or independence of γ t  and δ t.
 is an arbitrarily delayed Poisson process. We also give some corresponding results about characterizing the common distribution function F of the interarrival times to be geometric when F is discrete. Finally, we obtain some characterization results based on the total life or independence of γ t  and δ t.
Support for this research was provided in part by the National Science Council of the Republic of China, Grant No. NSC 80–0208-MI 10–06.