BMC Public Health 2009, 9:207 http://www.biomedcentral.com/1471-2458/9/207 EFvigaluuraetio1n design Evaluation design. health characteristics is available at LSOA level through the ONS' neighbourhood statistics gateway: http:// www.neighbourhood.statistics.gov.uk/dissemination/. Power calculations were carried out to ascertain the number of matched intervention and control clusters required to detect clinically important effect sizes for indi- cators of HE, HPA and MH. The primary outcomes of the interventions in the Well London project are: - For healthy eating a 50% increase in the proportion of adults (base estimate 27%) and a 30% increase in the proportion of children (base estimate 47%) who eat five or more pieces of fruit and vegetables a day. - For healthy physical activity, a 70% increase in the proportion of adults taking 30 minutes of moderate level physical activity 5 times a week (base estimate 18%); and - For mental health and wellbeing, a 30% increase in the proportion of the population achieving key thresholds on mental health and wellbeing indices. The baseline for this index can only be set following the first wave of the adult population survey. There is limited information available on these primary indicators at the LSOA level. Sample size calculations were therefore based on a number of indirect estimates. The baseline prevalence of HE in adults and children is from synthetic estimates derived from the Health Survey for England by the National Centre for Social Research and are presented at ward rather than LSOA level [21]. Using reasonable assumptions about the coefficient of variation between LSOA measures, an 80% power, the effect size given above and formula in Hayes [22] would require 5 pairs of matched clusters. For mental health the indicator used in the power calcula- tion was the 'per capita rate of claiming of incapacity ben- efit for reasons to do with mental health', this is available Page 4 of 11 (page number not for citation purposes)