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

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

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

*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.

ISSN: 1471-2458