. Author manuscript; available in PMC: 2013 Jul 1.

Published in final edited form as: Personal Disord. 2011 Aug 29;3(3):209–227. doi: 10.1037/a0025084

Table 1.

Descriptive Statistics and Gender Differences in Psychopathic Personality Traits and Environmental Variables

Psychopathic Personality Traits	Boys		Girls		F-value	Cohen’s d
Psychopathic Personality Traits	n	Mean SD	n	Mean SD	F-value	Cohen’s d
MPQ-Fearless Dominance	1115	53.2 8.9	1296	47.2 10.0	F(1,1242.38) = 179.42	.63^*
MPQ-Impulsive Antisociality	1115	52.3 9.3	1296	48.0 9.8	F(1,1228.50) = 87.04	.45^*
Environmental Variables
Academic Achievement & Engagement	1160	47.3 10.6	1293	52.4 8.8	F(1, 1257.12) = 108.22	−.52^*
Prosocial Peers	1072	50.5 10.2	1306	49.6 9.8	F(1, 1221.52) = 4.67	.09
Antisocial Peers	1025	52.3 11.0	1302	48.2 8.6	F(1, 1204.51) = 66.54	.42^*
Mother-child Relationship Problems	1169	51.1 10.0	1335	49.0 9.8	F(1, 1271.08) = 17.39	.21^*
Father-child Relationship Problems	1185	49.9 9.9	1314	50.1 10.0	F(1, 1258.35) = .03	−.02
Dependent Stressful Life Events: School and Legal Problems	1181	1.90 2.22	1332	1.38 1.53	F(1, 1275.84) = 33.45	.27^*
Independent Stressful Life Events: Family-level Problems	1184	2.64 2.89	1336	2.94 3.02	F(1, 1287.16) = 4.88	−.10^*

Note.

p < .001.

Dependent stressful life events are a count of the number of events reported by the participant. All other scores were standardized to a T-score metric with mean of 50 and standard deviation of 10. The test statistics are adjusted for the non-independence of the twin observations, which results in non-integer values for the degrees of freedom of the F tests.