Hi!   I am having trouble with running the GEE Repeated Measures weighted for missing data model.  I am getting: ERROR: Non-monotone missingness is not allowed. ERROR: Aborting modeling because of problems with input data. NOTE: The SAS System stopped processing this step because of errors.   I have complete data to dropout point which varies by patient of course. Some make it to six months and others to 24 months etc.  This is not random.  Fewer Controls made it into the second year and those patents were doing well when they dropped out.  I’m trying to model how our results vary if dropout status is used to weight those who dropped out early.   I have eliminated all patients only one dropout and even those with two.  Why the perpetual non-monotone error?  Baffled!   Thank you for any advice! Relana   ... View more