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Table 1 Sample size calculation

From: Study protocol for a randomized controlled trial comparing mindfulness-based cognitive therapy with maintenance anti-depressant treatment in the prevention of depressive relapse/recurrence: the PREVENT trial

Author Comparison Mean hazard ratio ICC Design factor** Attrition rate Sample size per groupa
Conservative scenario MBCT vs. m-ADM 0.63 .01 1.11 20% 210
Kuyken et al., 2008 [25] MBCT vs. m-ADM 0.63 -0.02 1.0 7%a 160
Ma & Teasdale, 2004 [22] MBCT vs. usual care 0.28 -0.008 1.0 3%b 14c
Teasdale et al., 2000 [23] MBCT vs. usual care 0.47 -0.04 1.0 5%b 41c
  1. Sample size necessary for 90% power at 5% significance at 24 months;
  2. a at 15 months; b at 60 weeks, cassuming exponential survival function.
  3. Note group size of 12