Table 3.

Ordinary least squares regression model results, overall and per cluster, for clicks per impression (C/I) given the intervention arm, optimization phase, and interaction between both terms.

Estimator clicks per impression (C/I)			Coefficient		SE	P value
Overall
	Constant	0.3257		0.014		<.001
	Intervention arm (β1)	0.0046		0.020		.82
	Optimization phase (β2)	–0.0091		0.020		.66
	Arm × phase (β1×β2)	0.2187		0.029		<.001
	R 2	0.490		N/A		N/A
	Adjusted R2	0.481		N/A		N/A
Cluster 1
	Constant	0.3266		0.031		<.001
	Intervention arm (β1)	0.0258		0.044		.56
	Optimization phase (β2)	0.0401		0.044		.37
	Arm × phase (β1×β2)	0.3683		0.063		<.001
	R 2	0.425		N/A		N/A
	Adjusted R2	0.416		N/A		N/A
Cluster 2
	Constant	0.5011		0.037		<.001
	Intervention arm (β1)	–0.0095		0.052		.86
	Optimization phase (β2)	–0.0017		0.052		.97
	Arm × phase (β1×β2)	0.2812		0.074		<.001
	R 2	0.191		N/A		N/A
	Adjusted R2	0.177		N/A		N/A
Cluster 3
	Constant	0.2719		0.022		<.001
	Intervention arm (β1)	–0.0125		0.031		.69
	Optimization phase (β2)	–0.0497		0.031		.11
	Arm × phase (β1×β2)	0.1387		0.044		.002
	R 2	0.090		N/A		N/A
	Adjusted R2	0.075		N/A		N/A
Cluster 4
	Constant	0.2876		0.024		<.001
	Intervention arm (β1)	0.0053		0.034		.87
	Optimization phase (β2)	–0.0156		0.034		.65
	Arm × phase (β1×β2)	0.0936		0.048		.05
	R 2	0.055		N/A		N/A
	Adjusted R2	0.039		N/A		N/A

^aN/A: not applicable.