# Re: st: booststraping in two stage models

 From "Danny Cohen-Zada" To Subject Re: st: booststraping in two stage models Date Tue, 11 Mar 2008 21:42:44 +0200

My first stage is OLS. I understand that you think it is ok to do it by hand.

Danny
----- Original Message ----- From: "Leonor Saravia" <lmisaravia@gmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Tuesday, March 11, 2008 9:21 PM
Subject: Re: st: booststraping in two stage models

```Hi Danny,

Maybe the problem is the model you are running in the first step. The
ivprobit command run a OLS regression in the first step (with the
instrument) and then predict the parameters that uses in the second
step, in which calculates the correct standard errors using bootstrap.
So, if your first step model isn't an OLS model, then the standard
errors are going to be different. Otherwise, I don't know what's
happening, sorry.

Hope this help,

Leonor

The ivprobit command in
```
Hi Leonor,

I did both ideas (with 1000 replications) and obtaind different standard
errors. Thus, i thought that maybe these two procedures are not equivalent.
Do you know what stata does when i use ivprobit, vce(boot)? Do you think
stata does what you told me to do by hand? If yes, why i obtained different
results?

Best,

Danny
----- Original Message -----
From: "Leonor Saravia" <lmisaravia@gmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Tuesday, March 11, 2008 8:26 PM
Subject: Re: st: booststraping in two stage models

> Danny,
>
> Stata has the ivprobit command, which allow you to calculate the
> bootstrapped standard errors. So you can estimate your model using it:
> ivprobit, vce(boot)
>
> Also, you can do it by hand:
>
> 1) estimate the first stage.
> 2) use predict, pp
> 3) estimate the second stage by probit (in which we substiture pp > instead
> of the endogenous regressor). Here you can use the - vce(boot) - option
>
> I hope this help,
>
> Leonor
>
>
>> Leonor,
>>
>> Thank you very much for the quick reply
>>
>> I am asking about the standard errors. How should i obtain the correct
>> standard errors of the second stage? Don't my procedure produce the
>> correct
>> standard errors?
>>
>> Thanks
>> ----- Original Message -----
>> From: "Leonor Saravia" <lmisaravia@gmail.com>
>> To: <statalist@hsphsun2.harvard.edu>
>> Sent: Tuesday, March 11, 2008 7:17 PM
>> Subject: Re: st: booststraping in two stage models
>>
>>
>> > Danny,
>> >
>> > The procedure you give is correct, you only need to correct the
>> > standard errors of the second stage.
>> >
>> > Leonor
>> >
>> > 2008/3/11, Danny Cohen-Zada <danoran@bgu.ac.il>:
>> >> I have a question that is relevant to all two stage models. For
>> >> example,
>> >> take the ivprobit model. If for any reason i want to obtian
>> >> bootstraped
>> >> standard errors. Can i do the following procedure.
>> >>
>> >> 1) estimate the first stage.
>> >> 2) use predict, pp
>> >> 3) estimate the second stage by probit (in which we substiture pp
>> >> of
>> >> the endogenous regressor) using the vce(boot) option.
>> >>
>> >> Will this be correct or should i bootstrapct the two stages >> >> together.
>> >> If
>> >> i
>> >> must bootstrapt the two stages together, how should i do it?
>> >>
>> >> thanks,
>> >>
>> >> Danny
>> >>
>> >>
>> >>
>> >> Department of Economics
>> >> Ben-Gurion University of the Negev
>> >> P.O.Box 653
>> >> Beer-Sheva 84105
>> >> Israel
>> >>
>> >> Tel: +972-8-6472301
>> >> Fax: +972-8-6472941
>> >>
>> >> http://www.econ.bgu.ac.il/facultym/danoran/main.htm
>> >>
>> >> *
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>> >
>>
>> *
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> *
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*
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```*
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```
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```