Table 2.

Summary of hierarchical regression analysis for sleep and circadian contributions to executive function

	F	R 2	R 2 Change	P	Beta	t	P	Collinearity (VIF)
Model 1	7.059	0.181	0.181	0.012
Sleep efficiency					0.425	2.657	0.012	1.000
Model 2	7.460	0.325	0.144	0.002
Sleep efficiency					0.405	2.742	0.010	1.003
Interdaily stability					0.380	2.573	0.015	1.003