[R-sig-ME] Estimating p-value for fixed effect which occurs also ininteraction

[Geoff Brookshire]

Here's a similar question from a few months ago, with Ben Bolker's
very helpful response:
https://stat.ethz.ch/pipermail/r-sig-mixed-models/2011q3/006690.html

cheers,
geoff

On Tue, May 8, 2012 at 7:37 PM, David Duffy <David.Duffy at qimr.edu.au> wrote:
> On Tue, 8 May 2012, Martin Heggli wrote:
>
>> Dear listers,
>>
>> I am evaluating an experiment in plant ecology. Since the experiment has
>> both crossed and nested random factors and the data are unbalanced, I
>> decided to use linear mixed effects models (lmer from lme4). Right now, I am
>> struggling to determine the significance of the fixed factors. I tried to
>> estimate the p-value for the fixed factors by dropping individual factors
>> from the model and comparing the two models with anova (cf. code below).
>> However, I run into trouble when I try to drop the factor Origin from the
>> model which occurs also in the Origin:Soil interaction term.
>
>
> The main effect of Origin gets absorbed by Origin:Soil ie you have only
> changed the interpretation.  If Origin:Soil is necessary to the model, you
> probably want to examine Soil within each level of Origin.
>
> Just 2c, David Duffy.
>
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