The probability of selection for the final community survey was related to the sampling frame which was determined by the expected parasite prevalence (which varies by age) in age categories; < 5 years, 5-15 years, > 15 years. Therefore, the age structure of the study population is not representative of the community population as a whole. Because we are looking at the community effect we will use inverse probability weights based on the age population structure of all clusters as recorded by the census survey. In practice, each individual will be assigned one of three weights, generated using the census survey, and based on their age as recorded at the final community survey. Population estimates of prevalence will be obtained using svy commands with the cluster as the primary sampling unit and age-related inverse probability weights. Children selected for the school survey were randomly selected after stratification by class. Households selected for the entomological survey were also randomly selected. No weighting is therefore required for the analysis of either the school or entomological surveys.