KME Method

Many times it is not possible to observe failure times on test. The times for those items, failures are not observed are said to be censored, but the amount of time it is observed functioning is noted. In this method, the reliability R (t_i) at failure time t_i is given by,

Where, n_i is the number at risk at time t_i and d_i is the number of failure time. It is common to regard t_n as an observed failure time even if that is not the actual situation. The total time on test is given by Eq. (28). The scaled TTT is evaluated and plot is drawn for observed failure times only.

Thus the survival function is R (t _i) = (n - 1) /n and TTT is referred to as

Thus the scaled TTT, φ_i  is equal to  S_i  /S_n and F_i is equal to i/n.