Re: st: Basic Q on Logistic Regression

[Richard Williams <Richard.A.Williams.5@nd.edu>]

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.


-------------------------------------------
Richard Williams, Associate Professor
OFFICE: (574)631-6668, (574)631-6463
FAX:    (574)288-4373
HOME:   (574)289-5227
EMAIL:  Richard.A.Williams.5@ND.Edu
WWW (personal):    http://www.nd.edu/~rwilliam
WWW (department):    http://www.nd.edu/~soc

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/