RE: Bootstrap resampling! -> Randomization test

From: "KOWALSKI, KENNETH G. [PHR/1825]" <kenneth.g.kowalski@pharmacia.com> Subject: RE: Bootstrap resampling! -> Randomization test Date: Thu, 29 Mar 2001 13:53:43 -0600 Nick, To add to what you are saying, simulations studies have shown that you get an inflated alpha (false positive error rate) when you simulate data and then fit a model that is different from the model you used to simulate data, ie., model misspecification. Stu Beal has pointed out that even the FOCE method runs into problems when the residual variance depends on the response such as Y=F*(1+EPS(1)) OR Y=F*EXP(EPS(1))+EPS(2) If we simulate data with residual variance structures as above then we will get inflated alphas even with FOCE...in this setting we need to use FOCE w/INTERACTION because there is an interaction between the etas (inbedded in F) and epsilons. However if we simulate and model the residual variance structure as Y=LOG(F) + EPS(1) then FOCE should work fine (i.e., there is no interaction between etas inbedded in F and EPS(1)) and not lead to inflated alphas assuming that other aspects of the model are specified correctly. Ken