For example, how to explain that the combined group is not more delinquent than the reactively aggressive group although they report more CU traits and more delinquent peers, two known factors in regard to delinquent behaviors?
Creating groups based on a cluster analysis may have created unnecessary problems. In particular, and contrary to what the authors seem to believe, it is not possible to know whether differences between the two aggressive groups reflect differences in levels of relational aggression or in type of relational aggression (reactive only vs. combined), given that the combined group is obviously much more aggressive than the reactive-only group. A better strategy would have been to predict each type of aggression while controlling its overlap with the other type (i.e., include reactive aggression when predicting proactive aggression and vice-versa).