The Healthy Lifestyles Programme (HeLP), a novel school-based intervention to prevent obesity in school children: study protocol for a randomised controlled trial

Table 2 Sample size scenarios based on differing assumptions

	ICC	Within person correlation coefficient	Attrition rate	Effect size detectable
				Number of SD units	Difference in BMI SDS^a
Base case	0.02	0.8	20%	0.19	0.25
Vary ICC	0	0.8	20%	0.14	0.18
	0.02	0.8	20%	0.19	0.25
	0.05	0.8	20%	0.25	0.32
Vary correlation between baseline and 24 months BMI SDS	0.02	0.75	20%	0.21	0.27
	0.02	0.8	20%	0.19	0.25
	0.02	0.85	20%	0.17	0.22
	0.02	0.9	20%	0.14	0.18
Vary attrition rate	0.02	0.8	10%	0.18	0.23
	0.02	0.8	20%	0.19	0.25
	0.02	0.8	30%	0.20	0.26

ISSN: 1745-6215