Table 5.

Fixed-effects for a mixed-effects linear model relating daily energy level from smartphone-measured and time variables. The ordinal variable for weekday was excluded from the near-maximal random-effects structure.

Fixed-effect	Estimate	Standard error	t value (degrees of freedom)	P value
Mean energy (intercept)	5.686	0.184	30.857 (53.9)	<.001
Day of study (semester)	−0.304	0.233	−1.303 (49.4)	.20
Day of week (coded 0-6, Monday-Sunday)	0.196	0.067	2.912 (1876.2)	.004
Sleep duration	−0.027	0.031	−0.858 (57.7)	.39
Daytime activity	0.182	0.039	4.673 (49.6)	<.001
Nighttime stillness	0.024	0.030	0.810 (50.4)	.42