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Re: st: dummy variable
From
Maarten Buis <[email protected]>
To
[email protected]
Subject
Re: st: dummy variable
Date
Fri, 16 Sep 2011 12:26:27 +0200
I guess any intro stats/econometrics book that discusses regression
will do, e.g Gujarati (1995) "Basic Econometric, third edition,
MacGraw-Hill, page 71. (This tells you when I had my intro
statistics/econometrics class...)
-- Maarten
On Fri, Sep 16, 2011 at 12:06 PM, Jing Zhou <[email protected]> wrote:
> Thanks a lot, Maarten. your suggestions are very appreciated. Can you
> please provide the reference of "The consequence of the fact that there
> are so few 1s is that the variance of the variable will be low, and thus
> the precision with which the effect of that variable is measured will
> also be low, i.e. large standard errors and confidence intervals."?
>
> Regards,
> Jing
>
>
>
>
>>>> Maarten Buis <[email protected]> 16/09/11 7:30 下午 >>>
> If you want to get results that control for that than you should add
> that variable, otherwise you should not do so. If you want to add that
> variable I would first try to find out why they are missing. For
> example, is there only one shareholder, and is it thus impossible for
> anyone to be the second largest shareholder or is the second largest
> shareholder unknown. In the former case you can set those missing
> values at zero (and possible add a dummy variable for single
> shareholder), while in the latter case you can think of multiple
> imputation (see: -help mi-).
>
> The consequence of the fact that there are so few 1s is that the
> variance of the variable will be low, and thus the precision with
> which the effect of that variable is measured will also be low, i.e.
> large standard errors and confidence intervals.
>
> Hope this helps,
> Maarten
>
> On Fri, Sep 16, 2011 at 10:51 AM, Jing Zhou <[email protected]>
> wrote:
>> Thanks Maarten, it measues whether the second largest shareholder of a
>> listed company is a state shareholder.
>>
>> Jing
>>
>>
>>>>> Maarten Buis <[email protected]> 16/09/11 6:02 下午 >>>
>> On Fri, Sep 16, 2011 at 2:09 AM, Jing Zhou wrote:
>>> I have a sample period from 2000-2009. now I am considering to add a
>> dummy variable into the regression. for the year of 2009, only 24 out
> of
>> 550 observations (<5%) valued at 1 of this dummy. for 2008, 31 out of
>> 502 observations (<5%) valued at 1. further, for the year of
> 2000-2002,
>> the missing value rate is 61.19%, 31.91%, and 13.33%, respectively.
> for
>> other variables of the regression, i can get relatively complete data
>> value of each observation. therefore, is it still necessary to include
>> this dummy in my regression? thanks!
>>
>> What is this dummy variable supposed to measure?
>>
>> -- Maarten
>>
>> --------------------------
>> Maarten L. Buis
>> Institut fuer Soziologie
>> Universitaet Tuebingen
>> Wilhelmstrasse 36
>> 72074 Tuebingen
>> Germany
>>
>>
>> http://www.maartenbuis.nl
>> --------------------------
>>
>> *
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>>
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>>
>
>
>
> --
> --------------------------
> Maarten L. Buis
> Institut fuer Soziologie
> Universitaet Tuebingen
> Wilhelmstrasse 36
> 72074 Tuebingen
> Germany
>
>
> http://www.maartenbuis.nl
> --------------------------
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
> *
> * For searches and help try:
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> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
--
--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany
http://www.maartenbuis.nl
--------------------------
*
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