Table II.

Simulation results (Set II) comparing correlation modeling (M) with conventional assumption of exchangeable correlation of constant magnitude (C). ECP is empirical coverage probability for 95% confidence intervals for β₁. Details of the simulation settings are provided in the text.

	ρ varying by treatment arm		ρ varying by cluster size
$\left(\begin{array}{cc}{\rho }_{c,\mathit{\text{sm}}}& {\rho }_{t,\mathit{\text{sm}}}\\ {\rho }_{c,\mathit{\text{lg}}}& {\rho }_{t,\mathit{\text{lg}}}\end{array}\right)$	$\left(\begin{array}{cc}0.05& 0.35\\ 0.05& 0.35\end{array}\right)$	$\left(\begin{array}{cc}0.35& 0.05\\ 0.35& 0.05\end{array}\right)$	$\left(\begin{array}{cc}0.05& 0.05\\ 0.35& 0.35\end{array}\right)$	$\left(\begin{array}{cc}0.35& 0.35\\ 0.05& 0.05\end{array}\right)$
Bias (M)	0.02	0.07	0.01	0.03
Bias (C)	0.01	0.07	0.02	0.04
Rel. Bias (M)	0.02	0.07	0.01	0.04
Rel. Bias (C)	0.02	0.08	0.02	0.04
Rel. Eff.	0.99	0.98	0.81	0.83
Rel. MSE	1.00	0.98	0.87	0.90
Emp. power (M)	0.82	0.81	0.92	0.88
Emp. power (C)	0.81	0.81	0.85	0.77
ECP (M)	0.96	0.95	0.95	0.95
ECP (C)	0.95	0.94	0.95	0.94