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Re: st: Box-Tidwell Test


From   lisenger@students.mail.uni-mannheim.de
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Box-Tidwell Test
Date   Tue, 26 Apr 2011 13:57:12 +0200

Hi


Ok I will try this. But I have another questions regarding testing the linearity assumption. Another way to check is the Locally Weigthed Scatterplot Smoothed (lowess) and the literature says that graphs with u- shaped and not continues shapes contravene the assumption.

I tried the test with:
lowess wabsunion themen, jitter(2) bwidth(.2)

and got as a result, a straight line, with some slope. It is for sure not s-shaped form as it is supposed to be, yet it is not u-shaped and continuous. So is it ok to write that the linearity assumption is ok? I know the case is special as I have 2 dummy variables with values (0-1), so its seems logical not to have a s-shaped graph, but I have to write something about linearity.

I am very sorry, i know my questions must seem totally stupid but this is the first time I use STATA and regression analysis.


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