Table 2.
Comparison of matched and non-matched samples (restricted to underage drinkers).
| Prior to Propensity Score Matching |
After Matching | |||||
|---|---|---|---|---|---|---|
| No Fake ID | Fake ID | p | No Fake ID | Fake ID | % bias reduction |
|
| Cross-sectional Sample | N=1454 (583 of which had fake IDs) | N=817 (359 of which had fake IDs) | ||||
| Age | 18.95 | 19.06 | .007 | 19.06 | 19.14 | 8.0% |
| Age of Alcohol Use Onset | 16.26 | 15.38 | <.001 | 15.13 | 15.35 | 78.6%* |
| Employed | .22 | .24 | .321 | .20 | .24 | NA |
| Exposure to Substance Use | 3.68 | 4.22 | <.001 | 4.28 | 4.25 | 94.7% |
| Family Income | 4.90 | 5.91 | <.001 | 5.87 | 5.87 | 99.2% |
| Gender (1=Male) | .42 | .50 | .002 | .52 | .49 | 75.6% |
| GPA | 3.00 | 3.02 | .466 | 3.11 | 3.05 | NA |
| Greek membership | .09 | .35 | <.001 | .33 | .38 | 81.3%* |
| Health (self-assessed) | 3.33 | 3.44 | .001 | 3.50 | 3.44 | 52.3% |
| Low Self-Control | 2.13 | 2.24 | <.001 | 2.25 | 2.24 | 86.0% |
| Peer Substance Use | 2.42 | 2.90 | <.001 | 2.94 | 2.93 | 98.2% |
| Race (1=Nonwhite) | .43 | .11 | <.001 | .12 | .10 | 94.9% |
| Rural Home Location | .34 | .38 | .114 | .47 | .38 | NA* |
| Sexual Orientation (1=LGBT) | .03 | .03 | .869 | .01 | .03 | NA |
| Subjective Distress | 3.07 | 3.05 | .608 | 3.06 | 3.06 | NA |
| Longitudinal Sample | N=2392 (510 of which had fake IDs) | N=518 (244 of which had fake IDs) | ||||
| Age | 18.31 | 18.34 | .340 | 18.34 | 18.34 | NA |
| Age of Alcohol Use Onset | 11.60 | 13.77 | <.001 | 13.94 | 13.95 | 99.8% |
| Employed | .41 | .31 | <.001 | .29 | .33 | 36.3% |
| Exposure to Substance Use | .14 | .16 | .494 | .11 | .15 | NA |
| Socioeconomic Status | .30 | .25 | .039 | .27 | .27 | 90.5% |
| Gender (1=Male) | .38 | .37 | .569 | .32 | .29 | NA |
| GPA | 3.10 | 2.95 | <.001 | 3.04 | 3.08 | 63.8% |
| Greek membership | .21 | .56 | <.001 | .56 | .55 | 97.0% |
| Health (self-assessed) | 3.91 | 4.04 | .001 | 4.04 | 4.04 | 98.4% |
| Low Self-Control | 17.34 | 16.70 | .062 | 15.48 | 15.66 | NA |
| Peer Substance Use | 2.54 | 3.72 | <.001 | 3.69 | 3.65 | 96.2% |
| Race (1=Nonwhite) | .11 | .06 | <.001 | .07 | .06 | 81.7% |
| Sexual Orientation (1=LGBT) | .06 | .05 | .657 | .02 | .03 | NA |
| Subjective Distress | .53 | .56 | .481 | .55 | .56 | NA |
Note: values listed are means of the groups prior to and following matching. Significant p values in the non-matched sample indicate those with and those without fake identification were different prior to matching. The percent reduction in bias is listed in the final column for each of the factors that were previously significantly different.
An * in the final column denotes the factors that remain significantly different between the groups even after matching.