Table 1.
Mean (SD) Intake Demographic Characteristics and Study Retention
| All participants | By experimental treatment |
||
| Noncontingent controls | Contingent | ||
| N | 116 | 40 | 76 |
| Age (years) | 37.0 (8.4) | 36.5 (8.2) | 37.9 (8.2) |
| Male (%) | 56 | 55 | 57 |
| African American (%) | 47 | 40 | 50 |
| Years heroin use | 10.3 (7.5) | 9.0 (5.8) | 10.6 (8.2) |
| Years cocaine use | 9.4 (7.4) | 9.1 (7.2) | 8.0 (6.5) |
| Days heroin usea | 29.0 (4.3) | 29.7 (0.9) | 29.2 (3.3) |
| Days cocaine usea | 17.4 (10.2) | 17.1 (10.6) | 17.5 (10.0) |
| Estimated IQ | 92.7 (8.1) | 92.9 (7.4) | 92.6 (8.4) |
| Years of education | 11.4 (1.3) | 11.5 (1.4) | 11.3 (1.3) |
| Monthly income ($) | 453 | 406 | 478 |
| Study retention (weeks) | 21.3 (6.4) | 22.0 (5.7) | 21 (6.8) |
| Completed 25 weeks (%) | 69 | 73 | 68 |
a
Number of days used in last 30 before admission to treatment.