Re: st: Correcting for self selection

[Alistair Windsor <alistair.windsor@gmail.com>]

Dear Erik,

Perhaps more information would be helpful.

It sounds to me like your unit is a project and not a company (is there 
one data point for each project submitted?). The outcome would then be 
that a given project wins. Projects submitted by (org a) type 
organizations may well individually have a lower chance of winning (as 
indicated by the negative coefficient). (org a) organizations may still 
have a high chance of winning a competition than (org b) organizations 
due to the greater number of projects that they submit.

Yours,

Alistair

On 1/29/11 1:33 AM, statalist-digest wrote:
> ----------------------------------------------------------------------
>
>  Date: Fri, 28 Jan 2011 08:50:42 +0100 From:erik.aadland@bi.no
> Subject: st: Correcting for self selection
>
> Dear statalist.
>
> Based on an unbalanced panel data set of organizations competing with
> projects in a monthly competition, I try to model the likelihood of
> an organization winning (binary outcome) given explanatory variables.
> However, the organizations with the highest scores on the main
> explanatory variables (orgs a) participate more often in the contest
> than organizations with lower scores (orgs b).
>
> Since (orgs a) participate often, they enter many projects that lose
> and some projects that win. As a consequence, even though (orgs a)
> win the most in the contest overall, the models produce negative
> coefficients for these (orgs a) organizations.
>
> Any suggestions for procedures in stata that I can apply to correct
> for this bias?
>
> Thanks,
>
> Erik. * *   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:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/