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Re: st: linear and quadratic trend analysis


From   Shelly Mahon <mdmahon@wisc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: linear and quadratic trend analysis
Date   Wed, 05 Mar 2008 11:41:48 -0700

David, 

Thank you for your response.  It is very helpful and much appreciated.

Shelly


Shelly Mahon
Ph.D. Candidate
University of Wisconsin-Madison
Human Development and Family Studies
1430 Linden Drive 
Madison, WI 53706-1575
email: mdmahon@wisc.edu



----- Original Message -----
From: David Jacobs <jacobs.184@sociology.osu.edu>
Date: Wednesday, March 5, 2008 10:19 am
Subject: Re: st: linear and quadratic trend analysis
To: statalist@hsphsun2.harvard.edu


> I'm not sure that Martin answered your question although you probably 
> 
> already know what I'm about to say.
> 
> To control for a linear trend simply construct a counter explanatory 
> variable running from 1 to how many years you have; to test a 
> quadratic, add the square of this explanatory variable and so on for a 
> cubic.
> 
> As analysis of variance allows continuous explanatory variables, this 
> 
> can be done in anova although most people probably would use 
> regress.  If you use a quadratic or cubic it would be a good idea to 
> test the relevant terms for joint significance.  That will help you 
> decide if the higher order term is necessary.
> 
> Dave Jacobs
> 
> At 03:49 PM 3/4/2008, you wrote:
> >Hi there,
> >I am conducting a study using the National AddHealth data 
> >set.  After running factorial anovas, it is clear that I need to 
> >follow up with a trend analysis.  I figured out how to run graphs, 
> >but does anyone have information on running the statistical tests 
> >for trends.  The study has four continuous outcome variables, plus 
> >sex, age, and grade level with one  categorical independent 
> >variable.  Any help is much appreciated.
> >Shelly
> >
> >Shelly Mahon
> >Ph.D. Candidate
> >University of Wisconsin-Madison
> >Human Development and Family Studies
> >1430 Linden Drive
> >Madison, WI 53706-1575
> >email: mdmahon@wisc.edu
> >
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