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Re: st: Binary Variables

From   Steve Samuels <>
Subject   Re: st: Binary Variables
Date   Wed, 2 Jun 2010 10:26:35 -0400

In addition to Neil's suggestions:

• show us the commands that created the regional indicators.

Do the omitted regions change, or is it just the four that you mentioned?

If the same four:

• tab -region- against the indicators for just those four regions.
• -sum-- your predictors & outcome for those four regions.
• run the regression with just the four "problem" regions
• try the -nocons- option on the regression restricted to the four


Steven Samuels
18 Cantine's Island
Saugerties NY 12477
Voice: 845-246-0774
Fax:    206-202-4783

On Wed, Jun 2, 2010 at 10:14 AM, Neil Shephard <> wrote:
> On Wed, Jun 2, 2010 at 2:03 PM, Natalie Trapp <> wrote:
>> Hi Neil,
>> I use Stata 11 and do a normal OLS estimation (with the "reg" command):
>> y = dependent variable (agricultural inputs)
>> x = independent variables (climate variables, crops, etc.) and dummy
>> variables that represent the 150 regions within the EU
> This is _not_ showing what you are typing, if you are using -regress-
> then I would expect you to have included something along the lines
> of....
> regress agricultural_inputs temperature crops i.region
>> The coefficients of the dependent variable within each region are very
>> divers and significant for about 120 regions.
>> My Problem is for instance, when "Schleswig Holstein" is my reference
>> group, Stata adittionally omits Valle d'Aoste, Vlaanderen and Ile de France.
> Could it be that there is missing data within your data structure such
> that most observations for these regions are omitted and the few that
> remain all have the same value of "agricultural_inputs".
>> Still, I don't quite understand why Stata does it, because the regions
>> (Germany, France, Netherlands) do not seem to be similar to me.
> "Seems" is a vague term and is based on your subjective interpretation
> of what you are expecting, and it need not be because you have the
> data, you can look at it.  Check the patterns of missing data that
> exist and how these pan out within the regions, in particular those
> that are being omitted.
> Stata will be omitting them for a reason (and it will often indicate
> why a particular category has been dropped).
> So again, pasting the _exact_ command you are entering and the
> resulting output would be very informative to other list members.  You
> can copy and paste from the Results window directly into an email.
> Neil
> --
> "... no scientific worker has a fixed level of significance at which
> from year to year, and in all circumstances, he rejects hypotheses; he
> rather gives his mind to each particular case in the light of his
> evidence and his ideas." - Sir Ronald A. Fisher (1956)
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