Hi, Suppose that we are building logit model using few independent variables. Event variable can be dichotomous or multinominal. Sometimes SAS prompts "Error: Complete Separation" or "Error : Quasi Separation". Its mean dependent Variable can be fully explain by any one independent Variable (Complete Separation) or can be fully explain by combinations of few independent variables ( Quasi Separation). Example 1 Event Age 1 25 1 45 1 30 0 18 0 24 0 9 0 21 1 40 0 16 1 60 This Shows Complete Separation becaus Event =1 for age > 24 Example 2 Event Age Height 0 16 160 0 18 130 0 24 178 0 21 145 0 45 120 1 38 160 1 55 150 1 30 169 1 40 170 1 25 170 This Shows Quasi Separation because Event =1 for age > 24 and Height>149. To remove Compete Separation or Quasi Separation, 1) find out variable those were responsible for Separation ( Check the Collinearity Matrix and Classification Matrix between dependent variable and independent variables) then 2) remove those variables or classify them in group so that Complete/Quasi separation no more exist. Hopefully this will help You. Thanks & Regards Ambrish
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