1)Maybe you missed some important independent variables . 2)Maybe the Scale for independent variable is too small . E.X. the dose of medication : 1ml v.s 100ml . Check PROC LOGISTIC 's UNIT statement. 3)Maybe there are some none-linear effect between independent variable and dependent variables. Check PROC LOGISTIC 's EFFECT statement. 4)Why not use Decision Tree or Random Forest in R ? ... View more