Table 4

Stepwise linear regression results for tar, nicotine, and carbon monoxide on cigarettes purchases in China, 2005–7 (n=78)

Variable	ΔR²	B	Beta	t	p Value
Tar
Intercept		−4.183		−0.796	0.429
Year	0.049	−1.274	−0.283	−4.455	<0.001
Ventilation	0.577	−0.118	−0.584	−7.675	<0.001
Tobacco weight	0.047	8.785	0.149	1.615	0.111
Filter weight	0.044	39.023	0.332	3.522	0.001
Paper permeability	0.016	−0.25	−0.112	−1.791	0.078
Rod length	0.010	0.160	0.192	1.683	0.097
Final model	0.721
Nicotine
Intercept		0.095		0.299	0.766
Year	0.008	−0.033	−0.098	−1.142	0.257
Ventilation	0.402	−0.007	−0.441	−4.351	<0.001
Tobacco weight	0.037	1.195	0.275	3.064	0.003
Filter length	0.053	0.012	0.277	2.778	0.007
Final model	0.472
CO (N=40)
Intercept		16.571		14.669	<0.001
Year	0.004	−0.183	−0.049	−0.429	0.67
Ventilation	0.477	−0.142	−0.713	−6.244	<0.001
Paper permeability	0.050	−0.040	−0.224	−1.988	0.054
Final model	0.493

B, unstandardised regression weight.
Beta, standardised regression weight.