Table 2.

Personal information of survey respondents.

Test	Gender	N	Age (M ±SD)	Household registration type
				Citie and town	Rural
First test	Male	178	20.12 ± 1.40	16.9%	83.1%
	Female	174	19.94 ± 1.12	20.1%	79.9%
	Total	352	20.03 ± 1.27	18.5%	81.5%
Second test	Male	517	20.15 ± 1.34	16.8%	83.2%
	Female	702	20.02 ± 1.34	20.9%	79.1%
	Total	1,219	20.09 ± 1.34	18.8%	81.2%