PC3 represented a notable exception to this trend. Despite its large correlation with P3, PC3 remained a significant determinant of group membership, across all externalizing diagnostic groups, when added to the model with P3. The chi-square difference was significant in all cases except the DAD group (p=0.13). Although this effect was not quite significant, PC3 showed the strongest effect of all the TF components in differentiating the small sample of DAD cases from controls. Further, P3’s contribution to group discrimination became non-significant when added to the model with PC3 for all diagnostic groups but ADHD. For ADHD, both PC3 and P3 amplitude made significant contributions, as the PC3+P3 bivariate model fit significantly better than either univariate model alone. In addition to PC3, PC2 was also able to significantly determine group membership in the presence of P3 for the ADHD and AAD groups.
