Based on parent and teacher ratings of primary school children on a scale comprising the 18 DSM-IV AD/HD symptoms, this study used confirmatory factor analysis to compare three models: all items in one factor; inattention in one and hyperactivity and impulsivity items in a separate factor; and inattention, hyperactivity, and impulsivity items in three separate factors. It also examined the prevalence rates of the three AD/HD Types, and gender and age differences. Results supported both the two- and three-factor models, with the three-factor model only slightly better than the two-factor model. Based on parent-teacher agreement, the prevalence rates were 1.6, 0.2 and 0.6% for the Inattentive, Hyperactive-Impulsive, and Combined Types, respectively. Overall, the male to female ratio was 5:1, and boys were rated higher than girls by both parents and teachers. Age differences were minimal. The implications of the findings in relation to some of the assumptions made in DSM-IV for AD/HD are discussed.
