. Author manuscript; available in PMC: 2005 Sep 21.

Published in final edited form as: Psychol Addict Behav. 2003 Mar;17(1):73–82. doi: 10.1037/0893-164X.17.1.73

Table 1.

Retention, Missing Urine Specimens, and Voucher Earnings

Variable	Control (n = 49)	CM only (n = 47)	CBT only (n = 48)	Combination (n = 49)	Analysis
Completed 12-week intervention	37 (76%)	38 (81%)	38 (79%)	34 (69%)	log-rank χ²(3, N = 193) = 2.63, p = 45.
Sporadically missing urine specimens during intervention
M (SD)	1.8 (2.2)	1.0 (1.4)	1.6 (1.8)	1.6 (1.8)	F(3, 189) = 1.96, p = .12
No. poor attenders (%)	5 (10%)	3 (6%)	5 (10%)	3 (6%)	Fisher exact p = .82
Mean voucher earnings (SD)	$283 (413)	$292 (386)	$182 (316)	$231 (374)	F(3, 189) = 0.89, p = .45
Median voucher earnings	$29	$64	$10	$10
Range of voucher earnings	$0–$1,153	$0–$1,155	$0–$1,155	$0–$1,155
Completed 12-week maintenance	31 (63%)	29 (62%)	28 (58%)	28 (57%)	log-rank χ²(3, N = 193) = 3.46, p = .33
Sporadically missing urine specimens during maintenance
M (SD)	1.8 (2.2)	1.0 (1.4)	1.1 (1.8)	1.9 (2.2)	F(3, 134) = 1.36, p = .26
No. poor attenders (%)	6 (12%)	6 (13%)	3 (6%)	5 (10%)	Fisher exact p = .72

Note. Poor attenders are participants missing 3 or more urine specimens not because of dropout. CM = contingency management; CBT = cognitive–behavioral therapy.