FIGURE 1.

Variance of the GLS estimator for the treatment-by-covariate interaction, ${\sigma }_4^2$, as a function of the, A, covariate ICC ρ_x and, B, adjusted outcome ICC ρ_y|x with cluster sizes m∈{20,50,100}, assuming ${\sigma }_{y\mid x}^2={\sigma }_x^2=1$, and ${\sigma }_w^2=1/4$