[R] A regression problem using dummy variables

rlearner309 unixunix99 at gmail.com
Wed Jul 2 15:38:05 CEST 2008

I think the covariance between dummy variables or between dummy variables and
intercept should always be zero.  meaning: no sigularity problem??

rlearner309 wrote:
> 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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