The latter. VC assumes that the variability in one location is independent of the variablity in another. For instance, appearance of lesions on the head are completely independent of lesions on the back. My natural inclination is that animals that are wound susceptible will have similar scores no matter where on the animal. If the relationship is anatomical, then some unstructured relationship is probably best. A heterogeneous compound symmetry structure might be appropriate (type=CSH). Take a look at the documentation for the type= option, especially the matrix representations and see if that might be an appropriate structure. Steve Denham
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