InvestorsHub Logo
icon url

PlentyParanoid

01/06/18 11:24 AM

#211756 RE: untohim #211750

Correct. And does not change anything I said. You are better off in understanding the mechanics of Kaplan Meier estimator by looking at its formula.


K(i) = K(i-1)*{1-n(i)/[N(i-1) - n(i) - c(i)]}
and
N(i) = N(i-1) - n(i) - c(i)

where
K(i): Kaplan Meier estimate at then end of period i
N(i): number of subjects at risk at the end of i:th period
n(i): number of events during i:th period
c(i): number of censors during i:th period

the term multiplying K(i-1) stays at 1 as long as there are no events, n(i) = 0, during the period. No change in estimate (should be intuitively clear, KM estimates failures like deaths. Censor is NOT a failure, so why should it register as one!).

Subject at risk, N(i), counts down with every event and censors. So, you can censor as many subjects as you like and they will not affect the value of Kaplan meier estimate as long as there are no subsequent events (one will do).