Apply the cluster design effect to an individually-randomised result

DE = 1 + (m - 1) * ICC (Machin 2018 Eq 12.5). Cluster-level rounding: n_clusters = ceiling(n_individuals_raw * DE / m), individuals = n_clusters * m. The raw (unrounded) individual count is used so that rounding happens once.

Usage

apply_cluster_design(base, cluster_size, icc)