[R-sig-eco] help

[lbp at njau.edu.cn]

Now I have difficulty to choose between two modelling approach. Here is th story. To examine the clutch size laid by a parasitic wasp into caterpillar hosts which varies in age and size, we exposed individual larvae of  three stages, after individually weighed, to parasitism, and the number of wasps emerged from each host (brood size) was recorded. Because host size and stage are mutually counfounding factors, the older the bigger, I have two modelling choices to separate the effect of stage and size. One is to make separate analyses, first analyzing the effct of stages in a model without the variable size, and then analyze the effect of the size under each stgae (several models); another approach is to make one analysis, put stage and size together in the same model to evaluate their separate and interacted effects on brood size.  For the later approach, the variable size actualy contains the inflormation about the stage, thus violating the independence assumation. I am wondering which appraoch is approriate.
   
   Thanks for any help. 

  Baoping




E-mail: lbp at njau.edu.cn
Phone: 86 (25) 84396394

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