Table 3.

Predictors of biomarkers of exposure

Predictors	Partial regression coefficient B	Standardized partial regression coefficient β	Significance probability p	95 % confidence interval for B
				Lower limit	Upper limit
Salivary cotinine (ng/mL)
Puff volume/day (mL)	0.01	0.27	<0.01	<0.01	0.01
Nominal brand nicotine yield (mg/cigarette)	214.32	0.44	<0.01	118.25	310.38
Self-reported smoking intensity	1.25	0.11	0.22	−0.74	3.23
Time to first smoking cigarette	−0.24	−0.18	0.05	−0.47	<0.01
CO in expiratory breath (ppm)
Puff volume/day (mL)	<0.01	0.27	0.01	<0.01	<0.01
Nominal brand nicotine yield (mg/cigarette)	2.35	0.09	0.40	−3.05	7.76
Self-reported smoking intensity	0.17	0.30	<0.01	0.06	0.29
Time to first smoking cigarette	−0.02	−0.19	0.03	−0.03	<0.01

Multiple correlation coefficient is r² = 0.275 (upper model) and r² = 0.239 (lower model), respectively