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Table 1 Sample size calculation

From: Cost and outcome of behavioural activation versus cognitive behaviour therapy for depression (COBRA): study protocol for a randomised controlled trial

Approach

MICD

Power

Attrition rate

Sample size per group*

50% BA-control effect size

1.90

90%

20%

220

50% BA-control effect size

1.90

80%

20%

160

LCI BA-control effect size

2.10

90%

20%

180

LCI BA-control effect size

2.10

80%

20%

135

Lower MCID

2.59

90%

20%

120

Lower MCID

2.59

80%

20%

90

  1. *Calculated assuming Patient Health Questionnaire 9 SD of 5.4 [33] and 1-sided 2.5% alpha using NQuery v7.0 MTE0-6, NQuery Statistical Solutions, 4500 Airport Business Park, Cork, Ireland. BA, behavioural activation; LCI, lowest confidence interval; MCID, minimum clinically important difference.