Table 2.

Descriptive statistics of subjects’ characteristics.

Variables	Types	Frequency	Percentage
Gender	Male	28	4.1
	Female	648	95.9
Only child in family	Yes	231	34.2
	No	445	65.8
Residence	Rural	307	45.4
	Township	191	28.3
	Urban	178	26.3
Origin types	NUEC	236	34.9
	Individual examination	267	39.5
	Five-year system	173	25.6