# Re: st: linear and quadratic trend analysis

 From Shelly Mahon 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
Human Development and Family Studies
1430 Linden Drive
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
>
>
> 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
> >Human Development and Family Studies
> >1430 Linden Drive
> >email: mdmahon@wisc.edu
> >
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>
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```