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From | David Hoaglin <dchoaglin@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: centred mean age |
Date | Wed, 30 Jan 2013 20:30:02 -0500 |
Nick's suggestion (below) is an important one. If the relation of your dependent variable to age is nonlinear, the first step should be to investigate the nature of the nonlinearity. If you have done that, and concluded that a single cubic polynomial is a reasonable description, OK. Often, mechanically adding a quadratic term (and a cubic term) to the model is not appropriate. Many people do that, and produce poor analyses as a result. Related to Rich's comment, in a multiple regression (or similar) model, the definition of each regression coefficient includes the list of all the other predictors. David Hoaglin On Wed, Jan 30, 2013 at 3:20 PM, Nick Cox <njcoxstata@gmail.com> wrote: > > All that said, there are quite possibly better ways of doing what you > want, such as cubic splines or fractional polynomials, which are well > supported in Stata. > > Nick * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/