Logistic regression and dummy variables PreviousNext
Mplus Discussion > Categorical Data Modeling >
 Ron McDowell posted on Thursday, May 05, 2011 - 7:53 am
I am fitting a logistic model where the dependent variable is categorical and has say, 5 levels such as 5 countries. If I use dummy variables to identify countries 2-5, I obtain estimates for the threshold for country 1 plus changes in the threshold for each of the remaining 4 countries. Can I fit the same model in a way equivalent to say, the noconstant option in STATA, where instead I get estimates/SE of the 5 country-specific thresholds as part of the output?
 Linda K. Muthen posted on Thursday, May 05, 2011 - 7:57 am
I think what you want is a multinomial logistic regression. You will obtain that if you put the dependent variable on the NOMINAL list.
 Ron McDowell posted on Sunday, May 08, 2011 - 8:25 am
I'm thinking more along the lines of the following example:

each subject is coded one if they are ill, 0 otherwise ('outcome'), with a dummy variable dummyUS=1 if from the US (0 otherwise), and dummyUK if from the UK (0 otherwise).

If I fit the logistic model
outcome ON dummyUK

the threshold will be -the estimated log odds of being from the US, and the coefficient for dummyUK will the change in the estimated log odds of being ill between UK and the US.

Can I fit a model analogous to the STATA commmand:

logit outcome dummyUS dummyUK, noconstant

so that there will be a coefficient for dummyUS (the estimated log odds of being ill in the US), dummyUK (the estimated log odds of being ill in the UK), and with no additional 'threshold' estimated in the model?
 Bengt O. Muthen posted on Sunday, May 08, 2011 - 8:20 pm
You can try


outcome on dummyUS dummyUK;

I don't know what will happen with those two covariates creating singularity, however.
 Ron McDowell posted on Tuesday, May 10, 2011 - 12:47 am
Thanks. That's what I am looking for.
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