[R] A regression problem using dummy variables

[Moshe Olshansky]

Do you have a reason to treat all 3 levels together and not have a separate regression for each level?


--- On Tue, 1/7/08, rlearner309 <unixunix99 at gmail.com> wrote:

> From: rlearner309 <unixunix99 at gmail.com>
> Subject: [R]  A regression problem using dummy variables
> To: r-help at r-project.org
> Received: Tuesday, 1 July, 2008, 11:38 PM
> This is actually more like a Statistics problem:
> I have a dataset with two dummy variables controlling three
> levels.  The
> problem is, one level does not have many observations
> compared with other
> two levels (a couple of data points compared with 1000+
> points on other
> levels).  When I run the regression, the result is bad.  I
> have unbalanced
> SE and VIF.  Does this kind of problem also belong to
> "near sigularity"
> problem?  Does it make any difference if I code the level
> that lacks data
> (0,0) in stead of (0,1)?
> 
> thanks a lot!
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