[R] 2x2 Contingency table with much sampling zeroes

Etienne Toffin etoffin at altern.org
Tue Oct 20 16:19:52 CEST 2009


I'm analyzing experimental results where two different events ("T1"  
and "T2") can occur or not during an experiment. I made my experiments  
with one factor ("Substrate") with two levels ("Sand" and "Clay").
I would like to know wether or not "Substrate" affects the occurrence  
probability of the two events. Moreover, for each condition I would  
like to test the heterogeneity of my experimental contingency table  
with a theoretical one (from simulations).

However, my problem is that several cells have sampling zeroes. My  
experiments can't be done again to fill these cells. Thus Chi-square  
requirements are not fulfilled and I have to find another statistical  

After spending hours searching for a solution, I thought I could use  
loglinear model to answer my questions, but :
- I'm not sure I can use loglinear model = do I fulfill the required  
conditions ?
- would this method answer to my hypothesis ?
- I not sure to really understand how I have to use loglin()…

Here is the data frame of my results.


What do you think of such datas ? Can I use any statistical method to  
test my hypothesis ? Any advice ?


Etienne Toffin

Etienne Toffin, PhD Student
Unit of Social Ecology
Université Libre de Bruxelles, CP 231
Boulevard du Triomphe
B-1050 Brussels

Tel: +32(0)2/650.55.30
Fax: +32(0)2/650.57.67

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