Experimental design of homogenization vs. heterogenization. The scheme of the experiment is in analogy to the study of Richter et al. ; 8 × 8 animals underwent 18F-FDG scans according to PET protocol 1. Varying experimental parameters were gender, age, and cage occupancy of the animals (n = 2 or n = 13 per cage). Animal groups were divided according to gender. This setup allowed for four strictly homogenized test group comparisons with the only parameter varying being gender (one example of such a comparison pair is indicated in dark gray). On the other hand, by reordering the same data into 8 × 8 randomized groups, four comparisons of such pseudo-heterogenized groups were performed (indicated by the light grey squares).