Percentage contribution of the mass-weighted population vectors (top to bottom) M_O, M_I, and M_Y, as measured in the different morphological classes, (left to right) EtG, EtS, and LtS galaxies. The red and blue curves are the density distributions for the HCG and CIG, respectively. The gray areas are the confidence interval models, assuming the two samples come from the same distribution. In each graph the curves are the continuous representation of the distribution. These curves were produced using the SM function in the R statistical package.