I am running a PROC LOGISTIC statement, defining the reference level under the class as: data have; input var1 var2 freq; cards; 0 1 1240 1 1 924 0 2 218 1 2 224 ;;;; proc logistic data=have; class var1 (param=ref ref='1'); model var2 = var1 / expb; freq freq; run; My contingency table looks like: Var1 Var2 | 1 2 ---------------------- 0 | 1240 218 1 | 924 224 Where I state the reference level of Var1 to be first , I mean it to be 1. This after all is the first level of variable Var1 . The odds ratio that is given however, is 0.725. That would imply the second level, 2, is taken as reference group.   odds ratio given: (924/1240)/(224/218)= 0.725   intended: (224/218)/(924/1240)= 1.379   Is this a matter of definition of reference group, or is the program not defining the reference level correctly? ... View more