Table 1.

The basic characteristics of the intervention group and control group

Variable	Kinds	Intervention group (n = 2065)		Control group (n = 2019)		x2	P
		Counts	Frequency (%)	Counts	Frequency (%)
Gender	Male	1131	54.77	1087	53.84	0.36	0.55
	Female	934	45.23	932	46.16
Age	10–13 years old	955	46.25	857	42.45	7.07	0.03*
	14–17 years old	926	44.84	988	48.94
	18–20 years old	184	8.91	174	8.62
Nationality	Han	2024	98.02	1998	98.96	6.10	0.02*
	Minority	41	1.99	21	1.04
Educational level	Primary school	838	40.58	795	39.38	1.96	0.38
	Junior high school	596	28.86	606	30.02
	Senior high school	631	30.56	618	30.61
Household register	Urban	1563	75.69	1168	57.85	146.65	< 0.01**
	Rural	502	24.31	851	42.15

Inference: ** p < 0.01; * p < 0.05