in particular , any CDF with position domain (suitable for life testing) is a special case of (2.1).For example,the weibull ,exponential,Rayleigh,compound weibull (Burr type XII),compound exponential(Lomax),compound Rayleigh,Pareto,beta,Gompertz and compound Gompertz distribution are all special cases of (2.1),see (17-19).