Table 5.
Main Effects for the Lottery-RDEC and MPT-Demand Indices in Predicting Cannabis Problems within Separate Zero-Inflated Negative Binomial (ZINB) Models
| Count Model | Zero-Inflation Model | |||||||
|---|---|---|---|---|---|---|---|---|
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| Lottery-RDEC Main Effect | Unstd. B | SE B | Z-value | p-value | Unstd. B | SE B | Z-value | p-value |
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| Year in College | .18 | .07 | 2.44 | .01 | .02 | .14 | .18 | .86 |
| Gender (female vs. male) | .02 | .20 | .13 | .90 | −.59 | .40 | −1.45 | .15 |
| Lottery-RDEC | −1.13 | 1.59 | −.71 | .48 | −821.71 | 366.18 | −2.24 | .02 |
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| Lottery-RDEC and MPT-Demand Indices | ||||||||
|
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|
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| Year in College | .21 | .08 | 2.74 | .006 | −.01 | .16 | −.03 | .97 |
| Gender (female vs. male) | −.00 | .19 | −.02 | .99 | −.29 | .45 | −.64 | .52 |
| Lottery-RDEC | −1.44 | 1.64 | −.88 | .38 | −374.86 | 257.31 | −1.46 | .15 |
| MPT-Intensity | .01 | .01 | .93 | .35 | −.02 | .04 | −.42 | .67 |
| MPT-Breakpoint | −.02 | .01 | −2.81 | .005 | .02 | .02 | 1.23 | .22 |
| MPT-Omax | .00 | .00 | .22 | .83 | −.07 | .03 | −2.32 | .02 |
| MPT-Elasticity | −.23 | .12 | −2.01 | .04 | −.39 | .22 | −1.76 | .08 |
Note. N = 284. Lottery-RDEC = Relative Discretionary Expenditures for Cannabis in the Lottery Task; MPT = Marijuana Purchase Task; Unstd. = unstandardized. In the zero-inflation component of each model, the likelihood of the dependent variable having a ‘true zero’ value is being predicted. Significant (p < .05) regression coefficients, and their associated Z-values, are bolded.