Table 2.

Definition of variables and descriptive results (n = 5,629).

Variable	Definition	Mean ± SD	min	max
Dependent variables
Depression score	Denotes the total depression score calculated from the CES_D scale.	14.608 ± 8.785	0	56
Depression	When score of the CES_D scale less than 16 is no depression, depression =0, 1 otherwise.	0.345	0	1
Independent variables
Times of activity	The times of activity times per week	2.208 ± 1.596	0	10
Hours of activity	The hours of activity per week	2.710 ± 2.974	0	20
Control Variables
Hours of sleep	The hours of sleep per day	9.739 ± 1.572	6	15
Boy	boy = 1, girl = 0	0.514	0	1
Grade	grade(four, five, seven, eight)	5.799 ± 1.571	4	8
Rural	Whether household registration is in a rural area, 1 for yes, 0 otherwise	0.834	0	1
Edufather	Father’s years of education	9.970 ± 2.584	0	16
Edumother	Mother’s years of education	9.834 ± 2.951	0	16

Mean indicates the mean value. SD denotes standard deviation.