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Table 4 Number of subjects needed to detect a relevant difference between DOiT and control schools

From: Exploring facilitating factors and barriers to the nationwide dissemination of a Dutch school-based obesity prevention program “DOiT”: a study protocol

Outcome sd Difference Number of subjects* Number of subject including 25% dropout
BMI 1.2 0.25 kg/m2 510 637
Waist circumference 3.9 2 cm 80 100
Sum of skinfolds 14.6 5 mm 180 224
Sugar-containing beverages 840.4 250 ml/day 238 297
Sedentary behaviour 147.5 30 minutes/day 508 635
Active transport 23.3 10 minutes/day 115 143
Snacks 1.4 1 portion/day 40 51
  1. *number of subjects required to conduct multi-level analyses with an estimated power of 90% and an alpha level of significance set at 0.05; sd = standard deviation based on the study of Singh et al. [12, 13]; BMI = Body Mass Index.