3.

不同性别、年龄居民吸烟起始时间

Initial time of smoking for male and female with different ages

Age (years)	Male				Female			X2	P
	≤15 years old	> 15 years old	Proportion of smokers stared smoking ≤15 years old (%)		≤15 years old	> 15 years old	Proportion of smokers stared smoking ≤15 years old (%)
40-60	62	1 073	5.46		0	55	0.00	2.160	0.142
61-80	29	486	5.63		4	35	10.26	0.004	0.949
> 80	0	39	0.00		0	6	0.00	-	-
Total	91	1 598	5.39		4	96	4.00	0.362	0.548