Table 4 summarizes results of chi-square difference tests comparing the corresponding univariate and bivariate models. In all cases, combining the TF component and P3 into the model offered improved ability to discriminate diagnostic from control groups, as demonstrated by positive chi-square differences between the univariate and bivariate models. In most cases, however, this improved group discrimination was not significant, indicating that the addition of the second variable into the model offered no significant additional discriminative value over the univariate model. Further, neither the TF component nor P3 was a better discriminator; neither accounted for significant additional variance in the presence of the other. These results were not surprising given the high correlations between P3 and the TF components.
