Table 2.
Intervention Group Differences on Alcohol Outcomes
| Outcome Measure | Contingent (N = 15) M(SD) | Noncontingent (N = 15) M(SD) | p-value | Cohen’s d (95% CI) |
|---|---|---|---|---|
| Primary Outcome | ||||
| Percent Days No Drinking Detected | ||||
| (counting “crossover” days as drinking days)a | ||||
| Baseline week | 19.1 (17.8) | 23.0 (17.7) | ||
| Intervention weeks | 54.3 (36.7) | 31.2 (28.9) | .053 | .74 (−.007–1.47) |
| (not counting “crossover” days as drinking days)a | ||||
| Baseline week | 39.0 (18.4) | 37.3 (19.8) | ||
| Intervention weeks | 65.7 (30.7) | 47.7 (27.2) | .083 | .67 (−.07–1.40) |
| Follow up (self report only) | 55.6 (25.2) | 56.2 (29.1) | .902 | .05 (.00–.31) |
| Secondary Outcomes | ||||
| Longest Number of Consecutive Days with No Drinking Detected | ||||
| Baseline week | 1.1 (1.2) | 1.3 (1.0) | ||
| Intervention weeks | 8.0 (7.5) | 2.9 (2.2) | .031 | .85 (.08–1.61) |
| Follow up (self report only) | 7.1 (5.9) | 5.7 (7.6) | .260 | .44 (−.32–1.18) |
| Peak TAC | ||||
| Baseline week | .191 (.111) | .198 (.073) | ||
| Intervention weeks | .189 (.123) | .241 (.094) | .200 | .48 (.00–1.18) |
| Follow up Peak eBAC (self report) | .145 (.082) | .184 (.101) | .625 | .20 (.00–.94) |
| Average Number of Drinks per Week (self report) | ||||
| Baseline week | 37.4 (20.3) | 40.8 (21.6) | ||
| Intervention weeks | 18.5 (18.9) | 30.2 (18.7) | .118 | .59 (.00–1.30) |
| Follow up | 19.0 (12.2) | 21.2 (18.9) | .895 | .05 (−.69–.79) |
Note. TAC = Transdermal Alcohol Concentration. eBAC = estimated Breath Alcohol Concentration. Peak TAC and Peak eBAC reflect the highest values across all collected days. Longest number of consecutive days with no drinking detected at follow up was square-root transformed for analyses; untransformed values are presented. Follow-up values reflect past 30 days. Regression analyses for intervention weeks controlled for baseline week values. Analyses for follow up (all self-report) controlled for baseline values from the Timeline Followback.
“Crossover” days were days when a TAC-identified drinking episode started on one calendar day and crossed over midnight into the next day. The two analyses in this table treated the second day of drinking differently, either counting it as a drinking day, or not.