Cluster Sampling Sample Size Calculation. If the DEFF and average number per cluster are provided the ICC is calculated using the formula ICCDEFF-1k-1. Mar 01 2004 For a completely randomized design to achieve the equivalent power of a patient-randomized trial standard sample size estimates require to be inflated by a factor 1 1 n 1ρ to accommodate for the clustering effect where n is the average cluster size and ρ is the estimated ICC assuming the clusters are of a similar size.
The VIF is then used as before to adjust the sample size for clustering. A mean score is an average score. DEFF 1 δ n 1 where DEFF is the design effect δ is the intraclass correlation for.
Z z score is directly tied to the confidence level and based on confidence level its values can be.
If the DEFF and average number per cluster are provided the ICC is calculated using the formula ICCDEFF-1k-1. The optimal number of clusters goes up and the optimal sample size per cluster goes down as the ICC goes up or as the cluster-to-person cost ratio goes down. The sample size formula is. DEFF1k-1ICC where k 30.
