https://communities.sas.com/t5/Statistical-Procedures/How-to-add-carryover-to-a-2x2-crossover-model/m-p/776059#M38009 <P>I am learning to do 2x2 crossover designs. carryover is coded with 2 levels. When period=1, carryover=X and when period=2, carryover=1.</P> <P>When I add carryover as a factor I am getting 0 df and SS's? Why? Please see code enclosed.&nbsp;</P> <PRE><CODE class=" language-sas">title 'table 3.6.3, page 75 Chou and Liu -Design and Analysis of Bioavailability and Bioequivalence Studies, Third edition';<BR />; <BR /></CODE></PRE> <PRE>proc glm data=mydata;<BR />class group subject tmt period carryover;<BR />model y=group subject (group) period tmt carryover /ss1 ss2 ss3 ss4 solution p;<BR />test h=group e=subject(group) / htype=3 etype=3;<BR />run;<BR /><BR /></PRE> <P>&nbsp;</P> Sun, 24 Oct 2021 11:42:03 GMT MaryA_Marion 2021-10-24T11:42:03Z https://communities.sas.com/t5/Statistical-Procedures/How-to-add-carryover-to-a-2x2-crossover-model/m-p/776059#M38009 <P>I am learning to do 2x2 crossover designs. carryover is coded with 2 levels. When period=1, carryover=X and when period=2, carryover=1.</P> <P>When I add carryover as a factor I am getting 0 df and SS's? Why? Please see code enclosed.&nbsp;</P> <PRE><CODE class=" language-sas">title 'table 3.6.3, page 75 Chou and Liu -Design and Analysis of Bioavailability and Bioequivalence Studies, Third edition';<BR />; <BR /></CODE></PRE> <PRE>proc glm data=mydata;<BR />class group subject tmt period carryover;<BR />model y=group subject (group) period tmt carryover /ss1 ss2 ss3 ss4 solution p;<BR />test h=group e=subject(group) / htype=3 etype=3;<BR />run;<BR /><BR /></PRE> <P>&nbsp;</P> Sun, 24 Oct 2021 11:42:03 GMT https://communities.sas.com/t5/Statistical-Procedures/How-to-add-carryover-to-a-2x2-crossover-model/m-p/776059#M38009 MaryA_Marion 2021-10-24T11:42:03Z