[R] Comparing three groups, data: present, absent

Mächler Marc Jacques marcm at student.ethz.ch
Thu May 20 17:39:11 CEST 2010

Dear R-Experts, Dear friends of dung.

I have a statistical Problem, to which nobody I asked could give me an answer. Maybe you can.

I was in the African-Savanna and made a Dung-Monitoring. This means I walked randomly over the field and for every Dung-Event I found I noted following parameters:

Species (Waterbuck, Giraffe, Reedbuck); 
Age-Category (less than a week, more than a week & less than a month, more than a month);
Termites present (0 or 1);

Now I want to compare for every species, if the percentage of Termites attack differ between the different Age-Categories

and if the percentage of attacks of Species differ between the same  Age-Categories.

I only found a lot of very complicated models for "Presence / Absence". But I do not need to find a treshold, I just want to compare groups. 

My Question now:

- What test do I have to use to compare groups.
- Do I have to transform the data (Termite.Attack which is 0 and 1)?

I really appreciate every hint.

Thanks a lot, 

Dung-Master Marc-Jacques from the swiss federal institute of technology 

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