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05/12/07 6:18 PM

#3515 RE: iwfal #3511

<if you have a low efficacy in a big trial (which you would have to have in order to get p near 0.05) then that lesser imbalance is still just as big as the efficacy.>

This is, of course true. But I am assuming that the efficacy effect is not small. Also Cox only corrects for imbalances that we know about, it cannot correct for factors that are not recorded. In theory at least, a reason for a large trial is to minimize the chance of missing some factor that might turn out to be significant and imbalanced.

In any case, how do you run MC with Cox without data on individual patients? Are you randomizing around the medians of the prognostic factors? What assumptions about the distributions in that case?