Re: st: Suest v/s biprob in stata 11

[Prakash Kashwan <pkashwan@umail.iu.edu>]

Hello Maarten (and apologies for misspelling your name in my previous email),
Thanks much for this explanation. From your explanation it seems as if
biprob accounts for the correlation between the residuals from
constituent models while suest does not (only when that is true, a
constrained biprob will give the same result as a suest, which has not
been constrained in the example you cite). Am I interpreting it well?
If this is indeed the case, it is problematic because the way stata
runs it, suest is a postestimation command, which is supposed to look
for correlation between the residuals. Am I to assume that suest is
not doing what it is supposed to do, and I should use biprob instead
of using suest?  What purpose does suest (as post-estimation command)
serve then?
I will appreciate these clarification.
Best Regards,
Prakash

On Mon, Jul 5, 2010 at 8:02 AM, Maarten buis <maartenbuis@yahoo.co.uk> wrote:
> --- On Sun, 4/7/10, Prakash Kashwan wrote:
>> I have a couple of queries regarding how suest works in
>> Stata 11. The new user friendly menus use biprob command,
>> which gives me different results compared to when I use
>> suest posestimation command - I wonder if biprob does
>> utilize the leverage offered by correlating residuals
>> of two models involved.
>
> Yes, you can see in the example below that when you
> constrain that correlation to 0, both -biprobit- and
> -suest- give the same estimates.
>
> *----------------------- begin example ------------------
> webuse school
> biprobit (private = logptax loginc years)     ///
>         (vote = logptax years)
> est store biprobit
>
> probit private logptax loginc years
> est store a
>
> probit vote logptax years
>
> est store b
> suest a b
> est store suest
>
> constraint 1 [athrho]_cons=0
> biprobit (private = logptax loginc years)      ///
>         (vote = logptax years), constraint(1)
> est store biprobit_constrained
>
> est table biprobit suest biprobit_constrained, ///
>    equations(1, 2)
> *-------------------- end example -----------------
> (For more on examples I sent to the Statalist see:
> http://www.maartenbuis.nl/example_faq )
>
> Note that -biprobit-, and many other Stata commands,
> maximizes the likelihood with respect to the Fisher's
> z transformation (or the inverse hyperbolic tangent
> of the correlation). This transformed correlation
> is stored in the parameter _cons in the equation
> athrho. The correlation is 0 when this transformed
> correlation is 0, so the appropriate constraint is
> -constraint 1 [athrho]_cons=0-.
>
> 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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>



-- 
-- 
Prakash Kashwan <http://mypage.iu.edu/~pkashwan/>
School of Public & Environmental Affairs (SPEA)
Workshop in Political Theory and Policy Analysis; Indiana University,
Bloomington
Research Fellow (2009) - International Foundation for Science (Sweden)

*
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