Membership in a particular P300 developmental group was tested for its association with familial risk status for each age group (8–12, 13–18, and 19–29) and gender combination using Wald tests. The Wald tests, which are provided by PROC TRAJ, account for uncertainty in trajectory group assignment. Neglecting group assignment uncertainty can lead to biased parameter estimates and biased standard error estimates (Roeder et al., 1999). Robust estimates of variance were used to account for family grouping.
