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Re: st: Tobit regression where left vs right censoring cannot be determined in the preferred dependent variable


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Tobit regression where left vs right censoring cannot be determined in the preferred dependent variable
Date   Mon, 17 Apr 2006 16:24:50 +0100 (BST)

Evan:
This prety much depends on the proportion of citties that are left censored. If that proportion is
small than I wouldn't bother doing anything fancy about it. If the proportion is large or if I was
feeling nerdish I would first model the raw number of people in poverty with -tobit- (strictly
speaking this assumes normality of the distribution of number of peoples in poverty which can't be
true, but since that count is likely to be large I don't worry about it.). Than I would create
multiple imputed values for the censored observations, and create proportions. Than I would model
that proportion with -betafit- (I couldn't resist the self plug) for each "completed" dataset, and
combine the different estimates using the standard multiple imputation equations. 
HTH,
Maarten

--- volpe@rhodes.edu wrote:
> Say that I've got the number of persons living in poverty.  As a raw number, this is left
> censored at 100.  Ideally, I want to look at the percentage of the population that is living in
> poverty.  So not only do I fail to have a constant censoring value but, for a given city with
> fewer than 100 persons living in poverty, I am not certain if that city is left censored or
> right censored....
>  
> Do you have any idea how to handle this? Would it be all too terrible to enter poverty = 100
> when poverty (raw) <100, and simply use OLS methods to analyze it?


-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


		
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