Bookmark and Share

Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: testing for significant changes in r squared within

From   Maarten buis <>
Subject   Re: st: testing for significant changes in r squared within
Date   Wed, 23 Feb 2011 14:29:36 +0000 (GMT)

--- On Wed, 23/2/11, Jan Mammen wrote:
> I would like to test the hypothesis of a nonlinear
> relationship by adding first a linear term, afterwards the
> squared and finally the cubic term of multinationality. I
> am looking for a possibility to show that the inclusion of
> the squared and cubic term significantly improves the model.

I addition to the comments made by Nick I'd like to add that
I like linear splines for such non-linearity tests. The big
advantage is that they are easiet to interpret than square
and cube terms and you are less likely to end up with 
improbable shapes than when you add a cube term.

You can make the spline terms using -mkspline-, see: 
-help mkspline-.

For the interpretation of spline terms, see:

You can test for linearity, by just using -test- on the 
hypothesis that the effects of the different terms are equal.

Hope this helps,

Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen


*   For searches and help try:

© Copyright 1996–2018 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   Site index