Table 4.

Prediction of Typical and Real-Time Marijuana Use by Relative Reinforcement Indices from Simulated Marijuana Purchasing Task

	Typical number of joints per marijuana use episodea		Real-time number of joints per marijuana use episodeb
Predictor	Δ R2	β	Δ R2	β
Step 1:
Demographic Variables	.30***		.28**
Sexc		−.25		−.12
Ethnicityd		−.51***		−.53***
Annual Income (Personal)		−.03		.01
Step 2: RRE Indices	.25**		.41***
Breakpoint		−.09		.09
Intensity of Demand		.22		.36**
Omax		.47**		.32*
Pmax		−.24		−.27*
Elasticity of Demand		−.09		−.32**
Adjusted R2	.46			.64

Notes. N = 48. Reduced N due to 10 individuals with missing breakpoint values. All reports of MJ joints were for average-sized joints (approx. ½ gram/joint). Participants who smoked MJ using other methods (e.g., bowl, bong, blunt) were trained to convert the quantity of MJ they smoked into average-sized joints. Observed values for Intensity of Demand, O_max, and P_max from the over-parameterized model were used in analyses. Regression coefficients represent results from each step prior to entry of subsequent steps.

^aMean of two items from the Marijuana Use Questionnaire and Marijuana Acquisition and Use Questionnaire.

^bBased on Interactive Voice Response (IVR) reports made just after marijuana use.

^cSex was coded 1 for male and 0 for female.

^dEthnicity was coded 1 for European American and 0 for non-European American (i.e., minority) background.

^*p < .05.

^**p < .01.

^***p < .001.