

Category independent variable 

Message/Author 

ting hlin posted on Wednesday, June 08, 2011  7:42 pm



Hi: i have a Category independent variable area (1=urban, 2 rural, 3 other), i run the models treating the variables as continuous varaibes, it converged, but i have trouble interpreting the results. then i tried 2 (1 v.s. 2 & 3) or 3 categories dummy coding for variables "area", it did not converge. i have specified number of iterations already. how should i handling the probelm? 


For a nominal variable with three categories, you should create two dummy variables. 


Dear Dr. Muthén, I am having difficulties with my dummycodes on a TYPE = TWOLEVEL COMPLEX design. My binary dependent variable is HAVEINS and my independent categorical variable is race_eth [Hispanic(1), white(2), Black(3), other(4)]. The frequencies for HAVEINS by race/ethnicity show that nonHispanic white have the highest rate. I dummycoded 3 Race variables in SAS(Ref. white)using the example below and also verified they all matched the original variable: If race_eth = 1 then hispanic = 1; else if race_eth = 3 or race_eth = 4 or race_eth = 2 then race_eth = 0; else race_eth = 999; When I run my model: HAVEINS ON hispanic black other; OUTPUT: CINTERVAL; The result indicate that Hispanic have higher rates of insurance, which is the opposite of what the frequencies show. To address this issue I decided to use the DEFINE command in Mplus: DEFINE: IF (race_eth == 1) then hispanic = 1; IF (race_eth /= 1) then hispanic = 0; IF (race_eth == 3) then Black = 1; IF (race_eth /= 3) then Black = 0; IF (race_eth == 4) then other = 1; IF (race_eth /= 4) then other = 0; My questions are: 1)Am I using the DEFINE command correctly? 2)Are the dummyvariables created using DEFINE matching the ones I created in SAS? Thank you. 


Try DEFINE: hispanic = 0; IF (race_eth == 1) then hispanic = 1; black = 0; IF (race_eth == 3) then Black = 1; other = 0; IF (race_eth == 4) then other = 1; Your SAS code talks about 3 or 4 and 2 so I don't think the above Mplus code can be correct. You don't mention 3 or 4 and you don't mention 2. 


Hi Dr. Muthen, Thank you very much for your quick feedback! I did created a dummy code for each variable, but I omitted the rest of the syntax due space constraints: If race_eth = 2 then white = 1; else if race_eth = 3 or race_eth = 4 or race_eth = 1 then white = 0; else white = 999; If race_eth = 3 then black = 1; else if race_eth = 2 or race_eth = 4 or race_eth = 1 then black = 0; else black = 999; If race_eth = 4 then other = 1; else if race_eth = 3 or race_eth = 4 or race_eth = 1 then other = 0; else other = 999; I included all variables except white in my model: HAVEINS ON hispanic black other; OUTPUT: CINTERVAL; 1) If I recode my dummy variables following your syntax suggestion, would I be matching the SAS dummy codes? 2) Is this the best practice to dummy code in Mplus? Thank you again, Oscar 


Your Define statement seems fine. I seem to recall that SAS codes its binary DV in the opposite way, but I may be wrong. 

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