Thank you very much for your many responses so far! >The reason for the confusion is that Bonnie presented the log likelihood >values with the wrong sign
I presented the values that SAS gives for log likelihood of my GENMOD models with a negative binomial distribution. (I only presented the largest and smallest AIC of a list of many possible models). log likelihood k AIC 532.5052 16 -1033.0104 509.8392 58 -903.6784 An (edited) response to explain why the positive values: [SAS reports only the 'pertinent part' of the likelihood; it leaves out constants that, if included, would result in the real likelihood and a negative log likelihood. Therefore, you can test which independent variables are significant, but you can't compare models fit with the negative binomial to models fit with the normal nor to models fit with the Poisson using the SAS output.] Is it OK to use this modified log likelihood in AIC? It sounds like, from most of the responses I received personally and on the list, that (if I decide to use AIC or AICc, which yielded the same order of models) I should choose the one with the smallest AIC, not the smallest absolute value of AIC. I am enjoying learning the different thoughts on if/how appropriate AIC is for ecological application. thank you! Bonnie _________________________________________________________________ Dont just search. Find. Check out the new MSN Search! http://search.msn.click-url.com/go/onm00200636ave/direct/01/
