Table 3

The effect of smoking ban at home and initiation of smoking among eighth grade students stratified by parental smoking behaviour. (N=901)

Stratified variables	Number	Per cent	Initiation of smoking
			Never smoker		Initiator		χ² test		Logistic regression
			Number	Per cent	Number	Per cent	χ²	p Value	OR (95% CI)	p Value
Paternal smoking^a*
Father with smoking (N=488)
HSR
No	383	78.81	335	87.47	48	12.53	χ²_(df=1)=0.0584	p=0.8091	1	p=0.8091
Yes	103	21.19	91	88.35	12	11.65			1.09 (0.55 to 2.13)
NK	2		2		0
Father without smoking (N=368)
HSR
No	216	59.50	189	87.50	27	12.50	χ²_(df=1)=7.5008	p=0.0062	1	p=0.0092
Yes	147	40.50	141	95.92	6	4.08			3.36 (1.35 to 8.35)
NK	5		4		1
Maternal smoking†
Mother with smoking (N=113)
HSR
No	94	83.93	68	72.34	26	27.66	χ²_(df=1)=0.2277	p=0.6332	1	p=0.6341
Yes	18	16.07	14	77.78	4	22.22			1.34 (0.41 to 4.44)
NK	1		1		0
Mother without smoking (N=755)
HSR
No	508	67.82	461	90.75	47	9.25	χ²_(df=1)=1.4487	p=0.2287	1	p=0.2311
Yes	241	32.18	225	93.36	16	6.64			1.43 (0.80 to 2.58)
NK	6		5		1

*Breslow-Day test for homogeneity of the ORs on paternal smoking, χ²_(df=1)=3.9404, p=0.0471.
†Breslow-Day test for homogeneity of the ORs on maternal smoking, χ²_(df=1)=0.0102, p=0.9195.
HSR, home smoking restriction; NK, not known.