Table 3.

Multiple regression models predicting bed time (hours) and wake time (hours) among respondents aged 15–17 in the 2003–2006 American Time Use Surveys. The coefficients represent the fraction of an hour (e.g. .50 = 30 minutes) associated with a one-unit change in the predictor.

	Bed time (hours)			Wake time (hours)
	Coefficient	95% CI	p value	Coefficient	95% CI	p value
Constant	21.43	20.36, 22.49	<.001	7.71	6.81, 8.60	<.001
DAY OF THE WEEK
Monday	reference			reference
Tuesday	−.09	−0.45, 0.27	.62	0.04	−0.27, 0.35	.80
Wednesday	−.08	−0.42, 0.25	.63	−0.02	−0.28, 0.24	.86
Thursday	−0.15	−0.48, 0.19	.39	0.26	−0.07, 0.58	.12
Friday	0.53	0.14, 0.91	.008	0.12	−0.30, 0.53	.59
Saturday	0.62	0.26, 0.98	.001	0.62	0.26, 0.97	.001
Sunday	0.01	−0.34, 0.35	.97	0.60	0.24, 0.95	.001
Year (per year after 2003)	−0.03	−0.10, 0.05	.43	−0.03	−0.11, 0.04	.33
Age (per year after 15)	0.15	0.04, 0.25	.008	0.05	−0.06, 0.15	.38
Female sex	0.25	.08, 0.42	.004	−0.07	−0.27, 0.13	.48
RACE
White	reference			reference
Black	0.40	0.11, 0.70	.007	−0.04	−0.30, 0.22	.75
Asian	0.28	−0.05, 0.61	.09	0.78	0.02, 1.54	.04
Hispanic	−0.20	−0.47, 0.06	.13	0.01	−0.24, 0.26	.93
Other race	0.13	−0.32, 0.58	.57	0.27	−0.26, 0.80	.32
ln(income)†	0.09	−.004, 0.19	.06	0.03	−0.05, 0.11	.43
ACTIVITIES (per hour)
Childcare activities†	0.17	0.05, 0.28	.005	−0.09	−0.28, 0.10	.36
Educational activities†	.05	0.01, 0.08	.007	−0.32	−0.37, −0.28	<.001
Social activities†	0.25	0.20, 0.30	<.001	−0.07	−0.13, −0.01	.02
Sports activities†	0.08	0.02, 0.14	.007	−0.14	−0.21, −0.07	<.001
TV watching†	0.15	0.10, 0.20	<.001	−0.05	−0.10, 0.01	.10
Work activities†	0.12	0.07, 0.16	<.001	−0.18	−0.24, −0.13	<.001
Computer use †	0.26	0.16, 0.37	<.001	0.04	−0.07, 0.16	.45

^†These variables were centered at their means.