Table 1.

Descriptive statistics

	TD % or mean (SD)	ID % or mean (SD)	χ2 (d.f.) or t (d.f.)	F (Levine’s test for equality of variances)
Child gender (% male)	55.9	59.4	χ2 =0.22 (1)
Child race (% minority)	38.7	46.4	χ2 =1.02 (1)
Family income (% <$50 000)	36.0	50.7	χ2 =3.78† (1)
Stanford–Binet IQ	104.3 (11.8)	60.0 (14.2)	22.62*** (178)	3.03†
Mother grade completed	15.7 (2.3)	14.4 (2.0)	3.85*** (178)	1.89
Father grade completed	15.7 (3.0)	14.6 (2.7)	2.23* (156)	0.38
Mother positive affect	2.26 (0.72)	2.01 (0.76)	2.19* (178)	0.21
Father positive affect	2.11 (0.86)	1.93 (0.83)	1.21 (144)	1.08
Mother negative affect	1.45 (0.61)	1.77 (0.80)	−2.86** (116)	11.48**
Father negative affect	1.24 (0.47)	1.35 (0.43)	−1.38 (144)	0.90
SSRS – cooperation‡	11.91 (3.27)	9.55 (3.56)	4.51*** (175)	1.45
SSRS – assertion‡	15.99 (2.75)	13.46 (3.88)	4.71*** (111)	9.99**
SSRS – responsibility‡	12.49 (3.21)	8.67 (3.83)	7.16*** (175)	2.49
SSRS – self-control‡	13.01 (3.21)	9.83 (3.69)	6.07*** (175)	1.02

Scores reported from child age 5 years except where otherwise noted. Child and mother variables had numbers of 111 TD and 69 ID except where otherwise noted. Father variables had numbers of 95 and 51 respectively.

^†P < 0.10,

^*P < 0.05,

^**P < 0.01,

^***P < 0.001.

^‡SSRS scores reported from child age 6 years, the first year they were collected. Three TD children did not have scores at age 6, so n = 108 TD and 69 ID for these analyses.

TD, typical development; ID, intellectual disability; SSRS, Social Skills Rating System.