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Re: st: Basic Q on Logistic Regression


From   Richard Williams <Richard.A.Williams.5@nd.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Basic Q on Logistic Regression
Date   Mon, 22 Dec 2003 08:44:41 -0500

At 03:43 AM 12/22/2003 -0800, azadeh1@socrates.berkeley.edu wrote:
Hello,

When using logit and logistic commands, can I have non-binary values for
my independent variable and controls? For example, for each
observation in my data set, I have the variable "age" and their ages (14,
15, 16...). If so, is there a limit on what the numbers can be or what form they can
take?
Azadeh, in general, whatever is legitimate for IVs in an OLS regression is legitimate in a logistic regression. That includes interaction terms. In your example, you are basically allowing the effect of age to differ by gender, which should be fine. (Which is not to say that your model is correctly specified, but there is no inherent reason you can't do things like this; incidentally I would code gender 0-1 if it isn't coded that way already).

Indeed, most things you can do in OLS seem to have a fairly straightforward logistic counterpart, e.g. hypothesis tests, transformations of the IVs, etc.; the most obvious exception is that you can't do transformations on the DV, e.g. take the log of Y. Interpretation is more confusing in logistic regression, but it is doable.


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