Table 1.

Descriptive statistics

	N	Mean	St. Dev.	Min	Median	Max
Infant attention, 7 months	1,193	17.68	2.47	4.50	18.00	24.00
Infant attention, 15 months	1,155	17.71	2.70	4.00	18.00	23.50
Infant attention, 24 months	1,116	17.63	3.15	4.50	18.25	24.25
Infant age, 7 months	1,201	7.73	1.48	5.03	7.56	15.38
Infant age, 15 months	1,169	15.75	1.35	13.50	15.38	22.34
Infant age, 24 months	1,144	24.89	1.95	22.24	24.31	35.38
Infant cortisol, 7 months	1,122	−1.84	0.77	−3.91	−1.93	1.54
Infant cortisol, 15 months	1,007	−1.95	0.84	−4.96	−2.09	1.59
Infant cortisol, 24 months	954	−2.05	0.80	−4.83	−2.13	1.55
Caregiver responsiveness, 7 months	1,182	0.81	0.20	0.09	0.82	1.00
Caregiver responsiveness, 15 months	1,155	0.87	0.17	0.09	0.91	1.00
Caregiver responsiveness, 24 months	1,104	0.90	0.16	0.09	1.00	1.00
Socioeconomic risk, 7 months	1,201	0.01	0.66	−2.24	0.01	1.98
Socioeconomic risk, 15 months	1,169	0.01	0.67	−2.75	0.07	2.00
Socioeconomic risk, 24 months	1,144	0.01	0.65	−2.57	0.05	2.17
Family conflict, 7 months	980	1.48	0.65	0.00	1.42	4.29
Family conflict, 15 months	932	1.38	0.61	0.00	1.28	3.88
Family conflict, 24 months	904	1.36	0.60	0.00	1.29	3.99
Learning materials, 7 months	1,179	0.84	0.21	0.00	0.89	1.00
Learning materials, 15 months	1,150	0.86	0.24	0.00	1.00	1.00
Learning materials, 24 months	1,072	0.89	0.18	0.00	1.00	1.00
Infant reactivity, 7 months	1,193	5.59	0.90	1.00	5.50	9.00
Infant reactivity, 15 months	1,155	6.03	0.96	2.00	6.00	9.00
Infant reactivity, 24 months	1,116	6.02	0.92	1.50	6.25	8.25
Economic stress, 7 months	1,188	2.29	0.70	1.00	2.17	4.33
Economic stress, 15 months	1,159	2.25	0.70	1.00	2.17	4.33
Economic stress, 24 months	1,125	2.19	0.70	1.00	2.17	4.33
Saliva sample time of day (hh:mm), 7 months	1,133	13:31	2:52	8:11	13.21	20:08
Saliva sample time of day (hh:mm), 15 months	1,070	13:57	2:54	8:45	13:43	20:24
Saliva sample time of day (hh:mm), 24 months	1,014	13:48	3:12	8:20	13:30	20:46