Table 5

Multiple linear regression analysis of the relation between cotinine concentration (ln) and smoking restriction type, survey year, presence of a parental smoker, family affluence and age, Scotland

	Coefficient	Linearised	t	p>t	95% CI
	Coefficient	standard error	t	p>t	95% CI
Parental smoking status
At least one parental smoker	1.201	0.107	11.19	<0.001	0.988 to 1.415
None	–
Survey year
2007	−0.693	0.071	−9.71	<0.001	−0.835 to −0.551
2006	–
Type of smoking restriction
Partial	0.405	0.098	4.13	<0.001	0.210 to 0.600
None	0.719	0.237	3.04	0.003	0.248 to 1.190
Complete	–
Family affluence
Low	0.411	0.061	6.70	<0.001	0.289 to 0.533
Medium	0.080	0.065	1.23	0.220	−0.049 to 0.210
High	–
Restriction type by survey year interaction
Partial× 2007	0.403	0.111	3.62	0.001	0.181 to 0.625
None× 2007	0.560	0.133	4.19	<0.001	0.295 to 0.825
(Complete restrictions and 2006 are reference categories)
Restriction type and presence of parental smokers interaction
Partial×at least one parental smoker	0.630	0.134	4.71	<0.001	0.364 to 0.896
None×at least one parental smoker	0.782	0.253	3.09	0.003	0.280 to 1.284
(Complete restrictions and no parental smokers are reference categories)
Age (years)	−0.080	0.067	−1.19	0.238	−0.214 to 0.054
Constant	−1.331	0.771	−1.73	0.088	−2.863 to 0.202