Diagnostic status was unknown for a small number of participants because they were disorder free at earlier assessments and did not participate at later occasions. Excluded were 36.2% of the 578 young men in this sample who had fathers who did not meet criteria for one of our externalizing groups and whose externalizing status would thus have been ambiguous. P300 was missing on some occasions because participants did not participate, because of computer or equipment problems, or because of poor task performance (i.e., >5 errors). Across the three paternal risk groups there were 1,107 potential P300 measurements (i.e., 3 assessments × [161 + 126 + 82 participants]). Of these, 30.4% were missing for one of the aforementioned reasons. The number of participants in each paternal risk group with usable P300 amplitude at each time point is presented in Table 3.
