Table 3.

Group cohesion and helping alliance scores

Variable	Standard care	CM	Significance test value (df), p-value	Effect size Cohen’s d
Week 1	n = 89	n = 87
Group cohesion	114.3 ± 17.0	119.5 ± 15.1	t (174) = 2.11, p < .04	.32
Helping alliance	88.7 ± 13.5	94.4 ± 12.2	t (175) = 2.93, p < .01	.44
Month 1	n = 73	n = 84
Group cohesion	113.5 ± 14.6	120.6 ± 17.5	t (155) = 2.73, p < .01	.44
Helping alliance	87.3 ± 17.3	96.7 ± 13.0	t (149) = 3.78, p < .001	.61
Month 2	n = 34	n = 42
Group cohesion	114.4 ± 18.1	118.7 ± 17.3	t (73) = 1.04, p = .30	.24
Helping alliance	89.5 ± 13.0	95.4 ± 15.1	t (71) = 1.77, p = .08	.42

Note: Sample sizes are based on patients remaining in group treatment session at each time point and completing the questionnaires; degrees of freedom differ at time points based on some incomplete assessments. CM=contingency management