Table 1.

Model fit indices for the two factor model (proactive–reactive aggression) and the one factor model (general aggression) and reliability indices for the RPQ total score, RPQ reactive and RPQ proactive subscales

	Two factor model				One factor model				Cronbach’s α
	χ 2	df	RMSEA	CFI	χ 2	df	RMSEA	CFI	Total	RA	PA
Total sample (N = 794)	955.70	229	.063	.931	982.33	230	.064	.928	.90	.85	.83
Dutch sample (N = 164)	336.85	229	.054	.950	398.44	230	.067	.922	.90	.85	.83
Moroccan sample (N = 215)	294.83	229	.037	.975	335.17	230	.046	.960	.88	.84	.81
Antillean/Surinamese sample (N = 156)	336.40	229	.055	.932	370.16	230	.063	.911	.88	.83	.79
Mixed ethnicity sample (N = 247)	350.39	229	.046	.958	420.70	230	.058	.934	.89	.84	.82

For 13 out of the 807 boys there were one or two missing RPQ item scores. These boys were not included in the factor analyses, but were included in all other analyses; For 12 boys information about ethnic origin were missing. These boys were not included in the factor analyses within the ethnic groups, but were included in all other analyses

CFI comparative fit index, RMSEA root mean square error of approximation, RA reactive aggression, PA proactive aggression