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# Re: st: tobit model in a percentage range

 From "Cremades, Roger" To "statalist@hsphsun2.harvard.edu" Subject Re: st: tobit model in a percentage range Date Wed, 17 Aug 2011 09:49:18 +0000

```Dear all,

I  see that betafit allows to display relative proportion ratios, reading help file I do not understand if they are the same as odd ratios?

How can I compare relative proportion ratios to odd ratios? (I am using -logit depvar vars ,or- with other dep vars with similar meaning and I would like to compare)

Thanks a lot Maarten and Tirthankar for your interesting and helpful suggestions,

Roger

De: Maarten Buis <maartenlbuis@gmail.com>
Para: statalist@hsphsun2.harvard.edu
Asunto: Re: st: tobit model in a percentage range

> On Tue, Aug 16, 2011 at 11:57 AM, Cremades, Roger wrote:
>> I am hesitating about using Tobit in a model with a dep var in a
>>  percentage range with values in 0 or 100 <snip>

On Wed, Aug 17, 2011 at 9:12 AM, Tirthankar Chakravarty wrote:
> Percentage and proportion data are modelled by so-called fractional
> response regression models <snip>

A fractional logit model can be estimated in Stata using -glm-
together with the -link(logit) vce(robust)- option, see Baum (2008).
Other alternatives are -betafit-, -zoib-, -dirifit- and -fmlogit-, all
available from SSC. I compared all these different models in this talk
at the 2010 German Stata Users' meeting:
<http://ideas.repec.org/p/boc/dsug10/04.html>.

Hope this helps,
Maarten

Ps. All these models model proportions rather than percentages, so you
need to divide your dependent variable by 100.

Christopher F. Baum (2008) "Stata tip 63: Modeling proportions" The
Stata Journal, 8(2): 299-303.

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
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