Spatial effects should be allowed for in primary care and other community-based cluster RCTS

Table 1 Results from a Dummy CRCT.

					AIC
Model	k	b(Treat)*	se	AIC	Difference
Treat + Random District + N/S	-	0.784	0.217	232.22	0
Treat + Random District + N/S + E/W	-	0.748	0.212	232.27	0.05
Treat + Random District + MM + N/S	1	0.786	0.212	234.02	1.8
Treat + Random District + MM + N/S + E/W	1	0.748	0.212	234.27	2.05
Treat + Random District + MM	1	0.753	0.203	236.34	4.12
Treat + Random District	-	0.491	0.262	247.86	15.64
Treat + N/S + E/W	-	0.592	0.116	285.20	52.98
Treat + N/S + E/W using robust se		0.592	0.233	285.20	52.98
Treat + N/S	-	0.613	0.117	287.65	55.43
Treat + N/S using robust se		0.613	0.246	287.65	55.43
Treat + robust se	-	0.247	0.260	361.18	128.96
True value		0.693	-	-	-

* expressed as log_e(hazard ratio) in all models, including % sun exposed (perc_aff) as a covariate

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