[R] Random effects aov

[Christine Griffiths]

Dear All

I have a repeated measures design in which abundance was measured 
repeatedly over 10 months in three treatments (Tortoise A; Tortoise B and 
control) established in 6 blocks, i.e. crossed fixed effects. My original 
design incorporated two tortoises per treatment, however as fieldwork goes 
I ended up losing some animals. Rather than lose a couple of enclosures in 
the analysis and have to do a lmer, I thought I could include tortoise 
weight as an explanatory variable. For my treatments, tortoise weight in 
the control always = 0, while in general Tortoise A is twice as large as 
Tortoise B except when I lost animals. Is this the correct model?

aov(Tel.ab~Tort.W+Treatment*Month+Error(Month/Block))

Or should tortoise weight be nested in Treatment, i.e not included as a 
fixed factor but including the fact that tortoises species may have an 
effect? I am utterly confused now as to whether that should be the case as 
to some extent Tort.W and Treatment are correlated.
Any help would be much appreciated.
Many thanks
Christine


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Christine Griffiths
School of Biological Sciences
University of Bristol
Woodland Road
Bristol BS8 1UG
Tel: 0117 9287593
Fax 0117 925 7374
Christine.Griffiths at bristol.ac.uk
http://www.bio.bris.ac.uk/research/mammal/tortoises.html