Table 10 Sample size calculations based on effect size estimates using trial data on the BADS and HADS-D, as well as a range of possible effect size estimates. Estimates do not include expected attrition. Power analyses were conducted based on the primary two-group comparison of interest. An alpha of 0.05 and a beta of 0.80 were used. BADS = Behavioural Activation for Depression Scale; HADS-D = Hospital Anxiety and Depression Scale-Depression

BADS total

N = 138 (69 per group)

N = 52 (26 per group)

N = 328 (164 per group)

HADS-D

N = 970 (485 per group)

N = 14 (7 per group)

N = 12 (6 per group)

Range of estimates of effect

Estimate

AP vs AE

AP vs WL

AE vs WL

 d = 0.30

N = 350 (175 per group)

N = 350 (175 per group)

N = 350 (175 per group)

 d = 0.40

N = 198 (99 per group)

N = 198 (99 per group)

N = 198 (99 per group)

 d = 0.50

N = 128 (64 per group)

N = 128 (64 per group)

N = 128 (64 per group)

 d = 0.60

N = 90 (45 per group)

N = 90 (45 per group)

N = 90 (45 per group)

 d = 0.70

N = 66 (33 per group)

N = 66 (33 per group)

N = 66 (33 per group)

 d = 0.80

N = 52 (26 per group)

N = 52 (26 per group)

N = 52 (26 per group)

 d = 0.90

N = 42 (21 per group)

N = 42 (21 per group)

N = 42 (21 per group)

 d = 1.00

N = 34 (17 per group)

N = 34 (17 per group)

N = 34 (17 per group)