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AW: st: Logistic Regression_Unequal Ns (outcomes)


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   AW: st: Logistic Regression_Unequal Ns (outcomes)
Date   Sun, 8 Mar 2009 15:58:01 +0100

<> 


Richard,

is -relogit- still under active development? Maybe it is so good it does not
need any fixes, but it was last touched in 1999. 

It is not to be found via -findit relogit-, and you cannot -net from- the
website you cite. The only way to get it is to unzip the files into the
PERSONAL directory... The point is that beginners have a hard time finding
it, and that is why the list has to alert them to it over and over...



HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Richard
Williams
Gesendet: Sonntag, 8. März 2009 16:43
An: statalist@hsphsun2.harvard.edu; statalist@hsphsun2.harvard.edu
Betreff: Re: st: Logistic Regression_Unequal Ns (outcomes)

At 08:34 AM 3/8/2009, Chao Yawo wrote:
>Hello, I'm preparing to run a logit model predicting the odds of NOT
>testing for an STD.  As you can see from the table below, 4688 (about
>98%) of respondents have my outcome of interest (i.e., have not tested
>for an STD).  I realized that because of this unequal groupings, all
>crosstabulations have higher proportions within the untested category.
>  I have a feeling that these could bias my estimates in a way. For
>example, given the unequal groupings, I think I am only restricted to
>modeling failure to test (the zero outcome), as modeling for ever
>tested (1) could lead to unstable estimates.  So my question is  what
>possible impact will this have on my model, and what can I do about
>it?  Thanks - Chao

Like Martin says, it doesn't matter which is one and which is 
zero.  Also, my experience is that the classification table, which I 
never use all that much anyway,  is especially worthless when you 
have such an extreme split.

You may wish to check into Gary King's -relogit-.  See

http://gking.harvard.edu/stats.shtml


-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME:   (574)289-5227
EMAIL:  Richard.A.Williams.5@ND.Edu
WWW:    http://www.nd.edu/~rwilliam

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