“…In specific, the use of general distributions for modeling this time variable has been highlighted. In this research direction, some authors have used Erlang, gamma, uniform, deterministic, hyper-Erlang, sum of hyper-exponentials, log-normal, Pareto, and Weibull distributions to model the pdf of CDT; see (Wang & Fan, 2007;Fang, 2001Rahman & Alfa, 2009;Pattaramalai et al, 2007Pattaramalai et al, , 2009Hidata et al, 2002;Thajchayapong & Toguz, 2005;Khan & Zeghlache, 1997;Zeng et al 2002;Kim & Choi, 2009) and the references therein. Fang in (Fang, 2001)) emphasizes the use of phase-type (PH) distributions for modeling CDT.…”