Table 5.

Frequency analysis of demographic variables

Variable	Classification	Frequency	Percentage (%)	SD
Gender	Female	443	49.6	0.5
	Male	451	50.4
Age	18 ~ 22 years old	562	62.9	0.748
	23 ~ 30 years old	228	25.5
	31 ~ 45 years old	87	9.7
	Under 45 years old	17	1.9
Education level	Junior high school	6	0.7	0.651
	High school	55	6.2
	Undergraduate	641	71.7
	Master	145	16.2
	PhD	47	5.3
Education level of parents	Junior high school	371	41.5	0.919
	High school	305	34.1
	Undergraduate	184	20.6
	Master	19	2.1
	PhD	15	1.7
Annual family income	Less than 50,000 RMB	183	20.5	1.023
	50,000-100,000 RMB	287	32.1
	100,000-200,000 RMB	251	28.1
	More than 200,000 RMB	173	19.3
Daily online time	Less than 2 h	91	10.2	0.978
	2–4 h	282	31.5
	4–6 h	265	29.6
	More than 6 h	256	28.6
Years of surfing	Less than 3 years	49	5.5	0.922
	3–6 years	236	26.4
	6–10 years	282	31.5
	More than 10 years	327	36.6