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Message-ID: <A4E5A0B016B8CB41A485FC629B633CED47A5ADAC43@GOLD.corp.lgc-group.com>
Date: 2012-10-05T12:54:05Z
From: S Ellison
Subject: Origins of difference in significance between lmer/pvals.fnc and aov?
In-Reply-To: <50573F9D.8020501@usc.edu>

> I have a data set which seems amenable to analysis either 
> through lmer or aov, so I am comparing their results. I'm 
> finding small p-values for the fixed effect of interest in 
> either case, but they differ quite a bit

One contributing factor is that if I read your output correctly, aov() is doing an F test using some quite low degrees of freedom (1?) for the top line, while lmer is testing a coefficient's t-statistic using (iirc) only the density degrees of freedom which is typically, if not always (?) the same as the residual dof. 

S Ellison
 

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