Table 3.

Estimated means for teacher-rated Attention Problems corrected for SES

Age	Twins			Singletons
	N	Mean	SE	N	Mean	SE
Boys
6	49	7.43	1.30	58	6.06	1.06
7	1,673	6.34	0.21	57	7.79	0.89
8	177	7.53	0.59	100	5.72	0.74
9	552	7.05	0.37	114	8.09	0.69
10	1,053	7.17	0.28	154	7.14	0.56
11	367	6.62	0.44	168	7.22	0.59
12	748	6.09	0.32	194	6.91	0.51
Girls
6	46	3.71	0.77	67	2.60	0.61
7	1,699	3.84	0.16	71	3.35	0.61
8	177	4.42	0.55	92	4.17	0.67
9	641	4.00	0.27	133	3.63	0.48
10	1,045	4.02	0.22	159	4.17	0.42
11	404	3.76	0.34	200	4.68	0.41
12	778	3.23	0.21	199	4.55	0.34*

Due to the longitudinal design, the N’s do not add up to the total number of children

N number of observations, SE standard error

* Significant twin-singleton mean difference (p < 0.001)