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Dear All, It seems that p-value generated by survdiff is too low for my plot. for such KM curves that cross each other (see attached), I didn't expect to get p-val = 0.03 (see result of survdiff below). Could you see where the discrepancy comes from? thanks ---------------------------------------------------------------------------------------------------------- > metInd = which (ds[,3] == 0) > print (survdiff(Surv (dsSurv[metInd], ds[metInd,4])~ifelse(pred.ds[metInd] < 0, 0, 1))) Call: survdiff(formula = Surv(dsSurv[metInd], ds[metInd, 4]) ~ ifelse(pred.ds[metInd] < 0, 0, 1)) N Observed Expected (O-E)^2/E ifelse(pred.ds[metInd] < 0, 0, 1)=0 125 1 3.22 1.53 ifelse(pred.ds[metInd] < 0, 0, 1)=1 69 4 1.78 2.78 (O-E)^2/V ifelse(pred.ds[metInd] < 0, 0, 1)=0 4.31 ifelse(pred.ds[metInd] < 0, 0, 1)=1 4.31 Chisq= 4.3 on 1 degrees of freedom, p= 0.0379 > plot (survfit(Surv (dsSurv[metInd], ds[metInd,4])~ifelse(pred.ds[metInd] < 0, 0, 1)))
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