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Re: st: Correcting for self selection

From   Alistair Windsor <[email protected]>
To   [email protected]
Subject   Re: st: Correcting for self selection
Date   Sat, 29 Jan 2011 13:18:26 -0600

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.



On 1/29/11 1:33 AM, statalist-digest wrote:

 Date: Fri, 28 Jan 2011 08:50:42 +0100 From:[email protected]
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?


Erik. * *   For searches and help try:

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