Hi, I am trying to use proc logit to predict a multinomial variable (polyshaptria) with 3 levels (1,2,3). The code is as follow: proc logistic data=triathlon_pct;
class polyshaptria;
model polyshaptria =pctPoly_bysurg age sex/ link=glogit;
output out=pred predicted=pred;
run;
quit; As polyshaptria has 3 level, I assume the predicted probability will distributed consistently with each level (sas will give three predicted probability for each polyshaptria level). That is if the polyshaptria is 1, SAS gives three probability for it corresponding to level 1,2,3. However, the predicted probability of level 1 is always larger than the other two levels. It doesn't make sense. See the data below: polyshaptria _LEVEL_ pred_prob 1 1 0.40541 1 2 0.37396 1 3 0.22063 1 1 0.39646 1 2 0.36705 1 3 0.23648 2 1 0.45166 2 2 0.44938 2 3 0.09896 For polyshaptria=2, pred_prob should get the largest when _level_=2. But it's still largest when _level_=1. Can anyone explain the reasons? How SAS predicted multinomial logistic model? Thanks, Andrea
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