Yes. Because the slopes are supposed to be the same. Level shifts are needed to be modeled.
Moshe Olshansky-2 wrote: > > 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 <[EMAIL PROTECTED]> wrote: > >> From: rlearner309 <[EMAIL PROTECTED]> >> Subject: [R] A regression problem using dummy variables >> To: r-help@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! >> -- >> View this message in context: >> http://www.nabble.com/A-regression-problem-using-dummy-variables-tp18214377p18214377.html >> Sent from the R help mailing list archive at Nabble.com. >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, >> reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > > -- View this message in context: http://www.nabble.com/A-regression-problem-using-dummy-variables-tp18214377p18230346.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
