https://communities.sas.com/t5/SAS-Health-and-Life-Sciences/Confidence-interval-for-OR-with-interactions/m-p/63760#M1527 Dear all,<BR /> <BR /> I am trying to compute confidence intervals for a logistic regression parameters with interactions. SAS automatically gives the intervals for the main effects but not for the interactions.<BR /> <BR /> I now that OR(A*B) = exp(effect A + effect B + effect(A*B)) but what about the confidence intervals?<BR /> <BR /> Regards!<BR /> Juan Vicente Tue, 02 Dec 2008 18:13:17 GMT JuanVte 2008-12-02T18:13:17Z https://communities.sas.com/t5/SAS-Health-and-Life-Sciences/Confidence-interval-for-OR-with-interactions/m-p/63760#M1527 Dear all,<BR /> <BR /> I am trying to compute confidence intervals for a logistic regression parameters with interactions. SAS automatically gives the intervals for the main effects but not for the interactions.<BR /> <BR /> I now that OR(A*B) = exp(effect A + effect B + effect(A*B)) but what about the confidence intervals?<BR /> <BR /> Regards!<BR /> Juan Vicente Tue, 02 Dec 2008 18:13:17 GMT https://communities.sas.com/t5/SAS-Health-and-Life-Sciences/Confidence-interval-for-OR-with-interactions/m-p/63760#M1527 JuanVte 2008-12-02T18:13:17Z https://communities.sas.com/t5/SAS-Health-and-Life-Sciences/Confidence-interval-for-OR-with-interactions/m-p/63761#M1528 The only way to get a CI on the interaction is to recode the data with the IA as a "main effect" <BR /> ABia=a*b;<BR /> and include it in the model as a separate variable.<BR /> <BR /> Although you can technically get a CI that way, it's nearly impossible to interpret. Good luck with that. If A &amp; B are binary, it's OK, but beyond that is a stretch. Tue, 02 Dec 2008 20:11:29 GMT https://communities.sas.com/t5/SAS-Health-and-Life-Sciences/Confidence-interval-for-OR-with-interactions/m-p/63761#M1528 Doc_Duke 2008-12-02T20:11:29Z