The Well London program - a cluster randomized trial of community engagement for improving health behaviors and mental wellbeing: baseline survey results

Table 7 Updated sample size calculations for the adult outcomes using the between-cluster coefficient of variation from the baseline survey (with missing responses multiply imputed)

Outcome	Baseline prevalence or mean (across all intervention and control clusters)	Km	Minimum detectable effect size	Expected effect size in original study design
Adults
Healthy eating	37% of adults eating at least five portions of fruit and vegetables per day	0.14	22% increase in prevalence	50% increase in prevalence
Physical activity	60% of adults doing at least five sessions of 30 min of moderate intensity physical activity per week	0.14	19% increase in prevalence	70% increase in prevalence^b
Mental health and wellbeing	18% of adults reporting feeling anxious or depressed	0.30	35% decrease in prevalence	-
	16% of adults reporting consulting their GP for emotional problems (anxiety and depression) in previous 12 months	0.23	41% decrease in prevalence	-
	Mean Hope Scale score = 4.6 (range, 1 to 6, higher score indicates better mental wellbeing)	0.03	Increase of 0.2 standard deviations	-

^aEffect sizes for binary outcomes are relative increases in prevalence.
^aCalculations are based on multiply imputed datasets; comparison to complete cases showed no substantial differences except in K_m for adolescent fruit consumption which decreased from 0.05 to 0.004.
^bBased on an expected baseline prevalence of 18%.

ISSN: 1745-6215