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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: Exp Clin Psychopharmacol. 2011 Apr;19(2):173–181. doi: 10.1037/a0023031

Table 1.

Demographic characteristics and baseline variables based on age category

Variable Age 18-29
(n=70)
Age 30-39
(n=186)
Age ≥ 40
(n=137)
Statistical test,
p value
Recruitment site (no., %) X2(6) = 5.12, p= 0.53
 Site A 5 (7.1) 16 (8.6) 10 (7.3)
 Site B 22 (31.4) 54 (29.0) 55 (40.1)
 Site C 21 (30.0) 61 (32.8) 40 (29.2)
 Site D 22 (31.4) 55 (29.6) 32 (23.4)
Treatment group (no.,%) X2(2) = 0.05, p = 0.98
 Contingency Management 20 (28.6) 54 (29.0) 41 (29.9)
 Standard Care 50 (71.4) 132 (70.1) 96 (70.1)
Studies (no., %) X2(4) = 6.30, p = 0.18
Petry et al. (2004) 25 (35.7) 62 (33.3) 33 (24.1)
Petry et al. (2005a) 23 (32.9) 70 (37.6) 49 (35.8)
Petry et al. (2006a) 22 (31.4) 54 (29.0) 55 (40.1)
Female (no.,%)* 32 (45.7)a 80 (43.0)a 85 (62.0)b X2(2) = 12.10, p = 0.003
Ethnicity (no.,%)* X2(6) = 30.80, p = 0.000
 African American 17 (24.3)a 110 (59.1)b 79 (57.7)b
 Caucasian 40 (57.1)a 51 (27.4)b 45 (32.8)b
 Hispanic 10 (14.3) 22 (11.8) 12 (8.8)
 Other 3 (4.3) 3 (1.6) 1 (0.7)
Marital status (no.,%)* X2(6) = 39.44, p = 0.000
 Never married 52 (74.3)a 109 (58.6)b 49 (35.8)c
 Married/Living with partner 13 (18.6) 32 (17.2) 30 (21.9)
 Separated/Divorced 5 (7.1)a 44 (23.7)b 54 (39.4)c
 Widowed 0 (0.0) 1 (0.5) 4 (2.9)
Annual income $9,580
(11,090)
$8,790
(16,410)
$10,820
(14,350)
F(2,390) = 0.73, p = 0.48
Years of education 11.5 (1.5) 11.5 (1.6) 11.8 (1.7) F(2,390) = 1.82, p = 0.16
Cocaine, opioid, or alcohol
positive sample at intake (no.,%)
15 (21.4) 32 (17.3) 26 (19.0) X2(2) = 0.59, p = 0.75
Past year DSM alcohol
dependence (no.,%)*
24 (34.3) 97 (52.2) 84 (61.3) X2(2) = 13.56, p = 0.001
Past month days of use
 Cocaine 4.7 (7.8) 3.7 (6.4) 3.0 (5.8) F(2,390) = 1.67, p = 0.19
 Cannabis* 3.7 (8.6)a 1.8 (5.7)b 1.0 (3.4)b F(2,390) = 5.49, p = 0.004
 Alcohol 1.1 (3.1) 2.7 (6.0) 2.8 (5.9) F(2,390) = 2.51, p = 0.08
 Opioids* 1.0 (3.6)a 0.1 (0.8)b 1.2 (4.7)a F(2,390) = 4.61, p = 0.01
No. of alcohol treatments* 1.0 (2.8)a 3.0 (7.0)a 6.8 (21.4)b F(2,390) = 5.08, p = 0.007
No. of drug treatments* 2.8 (5.5)a 4.6 (7.5)a 7.4 (13.6)b F(2,390) = 6.00, p = 0.003
No. of inpatient psychiatric
treatments
0.6 (1.5) 0.8 (1.7) 1.2 (3.3) F(2,390) = 2.06, p = 0.13
No. of outpatient psychiatric
treatments
1.4 (3.1) 1.2 (3.1) 1.1 (2.3) F(2,390) = 0.23, p = 0.79

Values represent means and (standard deviations) unless indicated.

*

Significant between group difference.

Different subscripts represent groups that differ significantly (p<.05) using Student Newman Keuls tests.