We examined several patterns of missing data to see whether paternal risk groups differed in rates of attrition. About a quarter of all families (24.8%) in these three groups had complete P300 data at all assessments for both sons. This rate did not differ significantly across paternal risk groups (27.6% of low paternal risk, 30.0% of intermediate paternal risk, and 18.2% of severe paternal risk groups), χ2(2, N = 201) = 2.06, p= .357. Furthermore, 42.6% of families had P300 data at all three assessments from one offspring and no more than one missing P300 measure from the other (48.3 % of low paternal risk, 44.3% of intermediate paternal risk, and 36.4 % of paternal AAB groups). The paternal risk groups did not differ significantly in this pattern, χ2(2, N = 201) =1.68, p= .432. Finally, the majority (61.2%) of families had at least two P300 measures from both offspring (66.7% of low paternal risk, 57.1 % of intermediate paternal risk, and 52.3 % of paternal AAB groups, a nonsignificant difference), χ2(2, N = 201) = 2.95, p= .229). In
