Sample size considerations The minimum difference of interest (MDI) is 10 minutes per day. After applying Bonferroni adjustment due to multiple comparisons in the three group trial and shared end-points, a total of 393 participants are needed using an sample SD of 25 minutes per day (30) with an α of 0.017 (two-tailed) to obtain a statistical power (1-β) of 80%. Allowing for an attrition rate of 30%, 513 patients (171 in each group) are allocated in the three arms.