Dear list
I'm trying to model the relationship between prey capture success by fish and fish size, density and velocity, but Im not sure which statistical method to use GLMM or GLM? Capture success was collected during trials that consisted in sending a prey every x min, which could be captured or not by individual fish. A total of 20 prey was send in each trial. Method A: GLMM I used fish.id as a random effect and the behavior of fish (0 no capture, 1- capture) as the response variable. One of my models looks like this: Model1<-glmer(capture~fish size + density velocity+(1|fish.id.),family=binomial,data=cap) Method B: GLM The response variable was the proportion of prey captured by each fish and one of my models: Model1<-glm(prop.capture~fish size + density velocity,family=binomial,data=cap) I used model selection using Akaike weights to examine the performance of each model. Results were similar with both methods, but I think I lose a bit of biological information if I use A: 1) I can't model average which may mean a loss of information when I have many interpretable models as I have with both approaches, 2) I lose the "fish size" effect which is an important bit of biological information (i.e. larger fish have higher capture success rates). However, A might be more appropriate for my type of data, even though Im not interested in variation within fish but among fish . Can anyone help? Thanks in advance! Joana Martelo, PhD Student Centro de Biologia Ambiental Departamento de Biologia Animal Faculdade de Ciências, Edificio C2,5ºPiso,Sala 2.5.15B 1749-016 Lisboa, Portugal <http://ffishgul.fc.ul.pt/> http://ffishgul.fc.ul.pt Por favor pense na sua responsabilidade ambiental antes de imprimir este email [[alternative HTML version deleted]]
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