Sample size {14}
malaria
MALARIA
The sample size is based on the main outcome (malaria incidence in a cohort of children followed prospectively in the cluster’s core area for six months), an outcome chosen based on WHO’s PPC for endectocides. This sample size has been corrected for cluster effect following Hayes and Bennett formula for unmatched rates [The magnitude (20% reduction) was selected based on WHO’s recommended PPC for endectocides [The final sample size is dependent on the population distribution as identified in the demography protocol.The number of children per cluster can vary in order to streamline the cluster generation once the demographic data is available. The power, significance level, and target effect size will remain unchanged. The final number of clusters depends on the cluster size (the number of children in the active pediatric cohort recruited in the core of all clusters).The target number of children to be included in every cluster is defined by the expected enrollment rate and loss to follow-up rate. We have estimated these as 15% and 20% respectively. So, for a cluster size to be 24 i.e., 24 children in the cohort finishing the study, the cluster must include 35 eligible children in the beginning (35 eligible of which an estimated 5 [15%] do not consent, 30 consent, of which 6 [20%] are LFU)The number of clusters required increases exponentially as the number of children per cluster (cluster size) decreases. This is particularly marked below 13 children per cluster. The number of children presented is the number of eligible children required at the beginning, not accounting for 15% non-consenting and up to 20% LFU.Peak incidence age: < 5 yearsPower: 80%Significance level: 5%Expected incidence in the control group (λ0): 4.20Expected incidence in the intervention (λ1): 3.36Incidence reduction: 20%Optimal cluster size: 20 children (assuming 3 non-consenting and 3 LFU)Follow-up time: 6 months starting post-community dosingCoefficient of variation (km): 0.35People treated per cluster: approximately 300Optimal total clusters required: 159 clusters (53 per arm)The final sample size may have to be adjusted as by the table below. However, the power and effect size will remain constant as does the ceiling of treatable adults (not to exceed 48,000 eligible adults).