Trajectory model selection involves the determination of an appropriate number of trajectory groups to fit as well as the estimation of parameters describing a polynomial relationship of P300 with age that will vary by trajectory group. Bayesian Information Criterion (BIC) was used as a goodness of fit measure to select the number of trajectory groups for each of the six gender – age range trajectory models. As an individual pattern of P300 measurements will not generally follow any identified group trajectory path perfectly, probabilities of individual membership in each group are provided by the model to reflect the inherent uncertainty in group membership.
