Table 1.

Notation for the intracluster correlations, between-period intracluster correlations, and cluster autocorrelations for each of the three models considered.

	Within-period	Between-period	Cluster
	intracluster correlation	intracluster correlation	autocorrelation
Model	$\text{corr}\left(Y_{kti},Y_{ktj}\right)$	$\text{corr}\left(Y_{kti},Y_{ksj}\right)$	$\frac{\text{corr}\left(Y_{kti},Y_{k\left(t+1\right)j}\right)}{\text{corr}\left(Y_{kti},Y_{ktj}\right)}$
Exchangeable	${\rho }_e$	${\rho }_e$	1
Block exchangeable	${\rho }_b$	$r_b{\rho }_b$	$r_b$
Discrete time decay	${\rho }_d$	$r_d^{|t-s|}{\rho }_d$	$r_d$

$Y_{kti}$ is the observation for participant i in period t in cluster k. We refer to ${\rho }_e$ as the aggregate intracluster correlation.