Re: Nested ANOVA

From: Bruce Weaver (bweaver_at_lakeheadu.ca)
Date: 11/19/04 

Date: Fri, 19 Nov 2004 14:52:05 -0500

jwalla wrote:

> Let me apoligise in advance if this is an elementary question, but some
> quick google group searches didn't address my question directly. I
> unfortunately wasted my mathematical education on Calculus instead of
> stats, so I'm having to play catch-up.
>
> How can I tell when a problem I'm working on requires nesting terms in
> ANOVA?

I'm not sure how to answer that other than saying, "When there is
nesting of one factor within another".

Perhaps it will help to think about the difference between one-way ANOVA
(with k independent groups of subjects) versus one-factor repeated
measures ANOVA. In one-way ANOVA, subjects are *nested* within groups.
  In one-factor repeated measures ANOVA, on the other hand, subjects are
*crossed* with treatments. This is why the one-factor repeated measures
ANOVA is often referred to as a Treatment x Subjects design.

> My stat software (Stata v8) makes the process of generating the
> analysis simple, but naturally I need to be able to present the problem
> properly. What is the consequence of leaving the nesting terms out of
> the model?

Staying with the same example, the consequence is that you don't have
the right model for the data--i.e., you would be doing a repeated
measures ANOVA when you don't really have repeated measures. And that
would be nonsensical.

HTH. 

-- 
Bruce Weaver
bweaver@lakeheadu.ca
www.angelfire.com/wv/bwhomedir

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