Table 1.

Demographic characteristics of the study sample (n = 462)

	Age 3 years assessment	Age 6 years assessment
Mean age of child, years (s.d.)	3.6 (0.3)	6.1 (0.4)
Mean age of mother, years (s.d.)	36.1 (4.5)	38.6 (4.5)
Mean age of father, years (s.d.)	38.4 (5.41)	40.8 (5.4)
Child sex: female, n (%)	212 (45.9)
Child race/ethnicity, n (%)
White/non-Hispanic	401 (86.8)
Hispanic	39 (8.4)
Black/African-American	7 (1.5)
Asian	9 (2.0)
Other	6 (1.3)
Child’s school status at second assessment, n (%)
Kindergarten		235 (50.9)
First grade		187 (40.5)
Second grade		20 (4.3)
Other		20 (4.3)
Interviewer respondents, n (%)
Biological mother	451 (97.6)	426 (92.2)
Biological father	8 (1.7)	35 (7.6)
Both parents	1 (0.2)	0 (0)
Grandparent	2 (0.4)	1 (0.2)
Biological parents’ marital status, n (%)
Married	435 (94.2)	413 (89.4)
Divorced, separated or widowed	9 (1.9)	32 (6.9)
Never married	18 (3.9)	17 (3.7)
Parents’ education: graduated college, n (%)
Mother	258 (56.7)	245 (59.3)
Father	209 (46.7)	195 (47.8)

s.d., Standard deviation.