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Re: st: too good to be true : lr test in mlogit?


From   Joerg Luedicke <joerg.luedicke@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: too good to be true : lr test in mlogit?
Date   Mon, 16 May 2011 09:38:33 -0400

Hi John,

Could you explain a little bit what your data looks like? It looks as
if you have observations nested within subjects, correct? What are
those observations and what are your subjects then? I have a slight
hunch that you want to run a 2-level model (Level 2 being whatever
your variable "id" is referring to, and Level 1 the however structured
 observations within "id") and that you are trying to predict an
outcome on Level 2 with Level 1 predictors or something like that.

J.

On Mon, May 16, 2011 at 7:11 AM, John Litfiba <cariboupad@gmx.fr> wrote:
> Dear Maarten yes the variable is correctly coded with 1 and 0 (you
> probably miss my previous mail ;-) )
> Thank you for the advice, I will contact the tech support to see whats
> wrong here
>
> Best Regards,
>
>
> On 16 May 2011 12:30, Maarten Buis <maartenlbuis@gmail.com> wrote:
>> On Mon, May 16, 2011 at 12:02 PM, John Litfiba <cariboupad@gmx.fr> wrote:
>>> Well, when I run a xtlogit (I first type xtset id, where id is the
>>> unique id for each of my individual in my database) with on year of
>>> data (1million) observations I get the message
>>>
>>> Yvar is categorical (Yes=1, No=0) and Xvar is also categorical
>>> (type1=1, type2=2)
>>
>> I would recode Xvar to such that type1 = 0 and type2 = 1:
>> gen byte type2 = Xvar - 1
>>
>> Remember that with fixed or random effects models you are making an
>> additional model for the group specific constants. It often helps when
>> these group specific constant refer to groups that actually occur in
>> the data.
>>
>> the logic of calling this variable type2 rather than Xvar is that the
>> value 1 is often associated with "true" and 0 with "false", so I think
>> of a variable named type2 as posing a question to each observation
>> "are you type2?", the answer being either true (1) or false (0).
>>
>> If recoding your explanatory variable does not work I would contact
>> Stata's techsupport, as these results suggest that there is something
>> logically wrong with the model you are trying to estimate, so ad-hoc
>> solutions like sampling from your data are not advisable until you
>> understand where the problem comes from. For how to contact Stata's
>> techsupport, see: http://www.stata.com/support/tech-support/
>>
>> Hope this helps,
>> Maarten
>>
>> --------------------------
>> Maarten L. Buis
>> Institut fuer Soziologie
>> Universitaet Tuebingen
>> Wilhelmstrasse 36
>> 72074 Tuebingen
>> Germany
>>
>>
>> http://www.maartenbuis.nl
>> --------------------------
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