Table 1.

Descriptive Statistics, Non-shared Variables, by MZ Twin Status

	Twins (Imputed, N=578)					Full Sample (Unimputed, N=20,715)
	Mean	SD	Range			Mean	SD	Range
Academic Outcomes
GPA*	2.84	0.76	1.0	-	4.9	2.75	0.77	1	-	4
PPVT	98.92	14.82	13	-	138	99.67	15.18	13	-	146
Behavioral & Attitudinal
Substance Use	1.17	1.86	0	-	8	1.29	1.97	0	-	8
Delinquency	0.11	0.18	0	-	1	0.12	0.19	0	-	1
Violence	−0.01	0.72	−1.9	-	5.5	0.00	0.66	−0.5	-	6.3
School Effort*	0.48	0.50	0	-	1	0.38	0.49	0	-	1
Parental Aspirations	7.63	2.96	0	-	20	8.01	2.33	2	-	10
College Aspirations	4.44	1.03	1	-	5	4.42	1.04	1	-	5
College Probability	4.15	1.13	1	-	5	4.13	1.16	1	-	5
No Breakfast	0.19	0.39	0	-	1	0.20	0.40	0	-	1
Extracurricular Participation				-					-
All Clubs	2.42	2.63	0	-	28	2.32	2.78	0	-	33
Academic Clubs	0.94	1.51	0	-	18	0.86	1.55	0	-	18
Network Structure				-					-
Density	0.46	0.33	−1.2	-	2.4	0.41	0.20	0.1	-	1
Centrality	0.78	0.69	0.0	-	4.8	0.78	0.65	0.0	-	4.3
Popularity*	4.84	4.05	0	-	23	4.32	3.64	0	-	32
Network Content				-					-
Interactions	12.46	10.48	−26	-	50	12.65	9.79	0	-	50
School Effort	3.22	0.62	0.6	-	5.5	3.24	0.41	1	-	4
School Difficulty	6.18	4.35	−14	-	27	6.29	2.62	0	-	16
Delinquency	8.06	7.32	−26	-	41	8.22	4.73	0	-	42
Race Heterogeneity	0.23	0.33	−1.5	-	1.6	0.26	0.23	0.0	-	0.8
Age Heterogeneity	0.39	0.32	−1.3	-	1.8	0.44	0.20	0.0	-	0.8
College Probability	6.43	2.44	−6	-	21	6.47	1.46	0	-	8
Middle Class Probability	5.12	2.22	−5	-	19	5.14	1.36	0	-	8

^*MZ-Full Sample t-test p<.05

NOTE: MZ twin values which are outside the full sample range are the result of imputation procedures.