Exploring all possible models

questions concerning analysis/theory using program MARK

Exploring all possible models

Postby chernan6 » Wed Mar 28, 2007 7:51 pm

Hi,
I am trying to figure if sea lion occupancy in some islands in the Gulf of California can be explained considering local environmental variables.
I recorded a number of variables (that I anticipated a priori to be relevant) at sites both occupied by sea lions and not used (I have data from 54 sites, 30 unused and 24 occupied).
Now I want to generate a set of candidate logistic regression models and use AICc criteria to explore which of these models (and thus environmental variables) explain the occupancy patterns best.
I have reduced my variables to a maximum of 7 in a global model, but that still leaves 127 possible models. My variables are: shade availability, substrate size, abundance of water pools, shoreline shape (angle), slope, substrate coloration, available resting area for sea lions.

My questions are:
1) Should I explore all of 127 models? If so what is the computationally efficient way to do this (I only know how to get AIC values for one model at a time)?
2) If not all should be explored? What could be the criteria for selecting fewer combinations? I feel all variables from those 7 are relevant.

Thanks in advance for your help!
chernan6
 
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