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Table 6 Sample size calculation for a future definitive trial

From: Results of a feasibility cluster randomised controlled trial of a peer-led school-based intervention to increase the physical activity of adolescent girls (PLAN-A)

Between-arms difference in weekday MVPA (mins) Power N students (uninflated) N students (inflated) N Schools
10 90 560 800 12
10 80 420 600 10
8 90 700 1000 16
8 80 560 800 12
6 90 980 1400 20
6 80 840 1200 18
  1. The following parameters were used: cluster size = 70, ICC on weekday MVPA = 0.01 MVPA standard deviation = 20 minutes, correlation between baseline and follow-up MVPA = 0.4, 5 per cent two-sided alpha and inflation to account for 30% of participants not providing primary outcome data.
  2. Values in boldface represent the sample size values proposed for the primary outcome in a future definitive trial