Hi,
I found two different formula for calculating the varicance of the
cumulative survival-rate (km-estimator).
#1: var(S)=S^2 * \sum[d/r(r-d)]
ist called Greenwood's formula
#2: var(S)=S^2*(1-S)/r
where
S: cum. survuval-rate
d: number of events
r: number of individuals at risk
I prefer formula #2. Is there any difference between this two formula?
Thanks for your help.
Bernd
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