. Author manuscript; available in PMC: 2017 Nov 1.

Published in final edited form as: J Exp Anal Behav. 2016 Nov;106(3):242–253. doi: 10.1002/jeab.228

Table 3.

Associations among empirical demand indices, derived demand indices based on the two-part mixed effects model, and smoking variables.

	Correlations

Demand indices	Intensity		Omax		Pmax		Breakpoint		α	CPD

	Empirical	Derived	Empirical	Derived	Empirical	Derived	Empirical	Derived

Empirical intensity	—	0.92^***	0.31^***	0.30^***	−0.03	−0.12^***	0.09^***	0.33^***	0.24^***	0.61^***
Derived intensity		—	0.30^***	0.30^***	−0.07^***	−0.13^***	0.06^**	0.34^***	0.24^***	0.62^***
Empirical Omax			—	0.82^***	0.48^***	0.37^***	0.51^***	0.74^***	−0.49^***	0.35^***
Derived Omax				—	0.41^***	0.41^***	0.44^***	0.82^***	−0.53^***	0.38^***
Empirical Pmax					—	0.41^***	0.59^***	0.44^***	−0.52^***	0.01
Derived Pmax						—	0.30^***	0.53^***	−0.80^***	0.02
Breakpoint (empirical)							—	0.45^***	−0.40^***	0.10^***
Breakpoint (derived)								—	−0.71^***	0.40^***
α (derived)									—	−0.03
CPD										—

	Comparing two nicotine dependence groups (high vs. low) in terms of demand indices

	Intensity		Omax		Pmax		Breakpoint		α

	Empirical	Derived	Empirical	Derived	Empirical	Derived	Empirical	Derived

^aT-test or log- rank test statistics	15.1^***	16.4^***	90.2^***	90.8^***	8.1^**	2.8	30.3^***	10.8^***	0.7

Note: CPD = cigarettes per day.

p < .05,

^**

p < .01,

^***

p < .001

T-test was used for intensity and derived breakpoint, and log-rank test was used for Omax, Pmax, and empirical breakpoint.