Where, mo =k = 1 mi m; is the number of failures within the time interval [t(f), t(+1)) mf 9f R(t(f)) (0,t(1)) 9o R(to)) {{to }} = is the unique failure time points ) (t(1), t(3)) 91 R(t(1)) (t(2), t(4)) m2 92 R(t(2)) R(ti)) is called the risk set and defined as [t(3), t(5)) m3 93 R(t(3)) R(t(i)) = #{j:to) 2 t} qi is the number of censored within the time interval = [t(k), 00) mk qk R(t(x)) SHOW THAT: R(t(i)) = Ejzi(m; +q;)