Dear R-experts A binary response is observed for patients receiving one of three different drugs injected in different doses. That is for each drug (treatment) we have a dose-response model. Additionlly the patient's age and gender is recorded. Initially I ran three logistic regressions, one for each drug type with gender as categorical variable and age and dose as continuous variables. If I want to know the effect of, say, gender on the response I now have three odds ratios - one for each dose response model. My question is: How can I compare the three odds ratios? Is it possible in R to combine the three dose-response models into a single model to get an overall estimate of the effect of age? Can I do something like lr <- glm(vom ~ therapy*age + therapy*gender + therapy*cisdose+therapy*cardose+therapy*cycdose,family=binomial,data=emrisk) Thanks in advance! Kim Mouridsen. _________________________________________________________________________ OFiR Spil - Vind 1.000 vis af kroner! Bes?g http://spil.ofir.dk OFiR Kontakt - Find en at dele julen med - Bes?g http://kontakt.ofir.dk