Table 1.

Example of differential clustering in a parallel cluster randomized trial

			First random	Second random	Residual variance,
	Log‐likelihood	Treat effect, SE	effect, SE	effect, SE	SE	ICC, 95% CI
No differential
clustering	−2100.47	0.111 (0.092)	0.195 (0.052)	1.288 (0 .026)	0.022 (0 .008, 0.062)
					Control	Intervention
Stratified model–control arm			0.304 (0.072)		1.236 ( 0.034)	0.057 ( 0.023, 0.134)
Stratified model–treatment arm			0.000 (0.000)		1.337( 0.039)		0.000 (0.000, 0.000)
Differential clustering models
Model 1—two separate random effects	−2097.09	0.098 (0.094)	0.000 (0.000)	0.296 (0.073)	1.285 (0.026)	0.050	0.000
Model 2—random interaction	−2100.47	0.111 (0.092)	0.000 (0.000)	0.195 (0.052)	1.288 (0.026)	0.022	0.022

Abbreviations: CI, confidence interval; ICC, intra‐cluster correlation; SE, standard error.