Table 2.
Outcome Variables at Follow up and Process Variables Pre and Post by Voucher Condition: Descriptive Statistics and Univariate Analyses (t-tests or Chi-square Tests)
| Variable | CV N (%) or Mean (SD) |
NV N (%) or Mean (SD) |
Effect Size d or OR |
95% CI |
|---|---|---|---|---|
| Confirmed 7-day abstinence2 | ||||
| 1 Month | 16 (9.3) | 13 (7.7) | 1.22 | 0.57, 2.63 |
| 3 Month | 9 (5.3) | 5 (3.0) | 1.81 | 0.59, 5.52 |
| 6 Month Follow Up | 6 (3.6) | 3 (1.8) | 2.03 | 0.49, 8.23 |
| 12 Month Follow Up | 6 (3.7) | 3 (1.8) | 2.08 | 0.51, 8.45 |
| Average no. cigarettes per day1 | ||||
| 1 Month Follow Up | 5.28 (5.49) | 7.98 (5.49) | −0.49* | −0.71, −0.27 |
| 3 Month Follow Up | 8.84 (7.57) | 9.89 (6.19) | −0.15 | −0.38, 0.08 |
| 6 Month Follow Up | 10.87 (8.05) | 12.18 (6.59) | −0.12 | −.057, 0.33 |
| 12 Month Follow Up | 11.67 (7.70) | 12.78 (7.23) | −0.15 | −0.40, 0.11 |
| Percent smoking days1 | ||||
| 1 Month Follow Up | 77.51 (33.02) | 88.33 (25.48) | −0.37* | −0.59, −0.15 |
| 3 Month Follow Up | 82.39 (30.63) | 88.40 (25.48) | −0.25 | −0.46, 0.02 |
| 6 Month Follow Up | 88.49 (26.45) | 92.30 (21.91) | −0.16 | −0.40, 0.08 |
| 12 Month Follow Up | 87.38 (26.62) | 91.53 (22.86) | −0.17 | −0.42, 0.09 |
| Relapse to any heavy drinking2 | ||||
| 1 Month Follow Up | 12 (7.4) | 8 (5.1) | 1.48 | 0.59, 3.72 |
| 3 Month Follow Up | 23 (15.5) | 24 (16.8) | 0.91 | 0.49, 1.70 |
| 6 Month Follow Up | 38 (27.5) | 35 (26.9) | 1.03 | 0.60, 1.77 |
| 12 Month Follow Up | 38 (30.2) | 36 (31.6) | 0.94 | 0.54, 1.62 |
| Number of drug use days1 | ||||
| 1 Month Follow Up | 1.46 (2.60) | 0.36 (0.51) | −0.01 | −0.23, 0.21 |
| 3 Month Follow Up | 3.35 (10.32) | 3.87 (12.13) | −0.01 | −0.24, 0.22 |
| 6 Month Follow Up | 7.25 (17.21) | 8.69 (20.20) | <0.01 | −0.23, 0.25 |
| 12 Month Follow Up | 21.55 (41.71) | 21.82 (43.24) | 0.02 | −0.23, 0.28 |
| Relapse to any drug use2 | ||||
| 1 Month Follow Up | 13 (8.0) | 16 (10.2) | 0.76 | 0.36, 1.65 |
| 3 Month Follow Up | 38 (49.1) | 32 (50.9) | 1.19 | 0.67, 2.06 |
| 6 Month Follow Up | 50 (36.2) | 42 (32.3) | 1.19 | 0.72, 1.97 |
| 12 Month Follow Up | 54 (42.9) | 50 (43.9) | 0.96 | 0.58, 1.60 |
| Contemplation Ladder1 | ||||
| Pretreatment | 5.40 (1.63) | 5.31 (1.55) | 0.06 | −0.17, 0.29 |
| 1 Month Follow Up | 7.28 (1.73) | 6.89 (1.65) | 0.23 | 0.00, 0.46 |
| Self- Efficacy for Smoking Abstinence1 |
||||
| Pretreatment | 1.78 (0.76) | 1.67 (0.70) | 0.15 | −0.08, 0.38 |
| 1 Month Follow Up | 3.10 (1.03) | 2.83 (1.03) | 0.26 | 0.03, 0.49 |
*
p < .001
Note: Sample size for continuous variables at 1 month n = 163 in CV and n = 158 in NCV, at 3 months n = 148 in CV and n = 143 in NCV, at 6 months n = 138 in CV and n = 130 in NCV, and at 12 months n = 126 in CV and n = 114 in NCV.
CV = contingent vouchers condition; NV = noncontingent vouchers condition ; CI = confidence interval
1
Normally distributed variable; effect size is in standardized units of the dependent variable (d).
2
Dichotomous variable; effect size is expressed as an odds ratio.