Table 4.

Submitted samples of the primary and secondary target drugs

	STA (32) % (n° of samples)	STCM (33) % (n° of samples)	t-value*	p-value
Total Samples Submitted
Crack/cocaine	9.8 (113)	52.9 (628)	4.286	0.0001
THC	10.3 (119)	53.5 (636)	4.206	0.0001
Alcohol	9.8 (113)	54.2 (644)	4.310	0.0001
Negative Samples Submitted (considering all expected samples)
Crack/cocaine	8.3 (96)	46.5 (552)	4.138	0.0001
THC	9.8 (113)	50.3 (598)	3.906	0.0001
Alcohol	9.4 (108)	53.9 (641)	4.408	0.0001
Negative Samples Submitted (considering submitted samples only)
Crack/cocaine	89.2 (96)	87.8 (552)	−0.872	0.386
THC	93 (113)	92.6 (598)	−0.112	0.911
Alcohol	98.4 (113)	99.7 (641)	1.075	0.287

^*the reference group is the Standard Treatment Alone condition.

Abbreviations: STCM, Standard Treatment plus Contingency Management; STA, Standard Treatment Alone; THC, tetrahydrocannabinol.