Table 2

Odds ratios (95% confidence intervals) for response per $0.01 increase in incentive in 82 trials that evaluated unconditional incentives, stratified by the minimum and maximum amounts given in each trial

	Maximum amount
	$0.00–0.49	$0.50–0.99	$1.00–1.99	$2.00–4.99	$5.00 +
*The p values shown are from the χ² test for heterogeneity among trial results within strata.
Minimum amount
$0	1.012	1.010	1.005	1.003	1.001
	(1.006, 1.017)	(1.008, 1.012)	(1.004, 1.007)	(1.002, 1.005)	(1.001, 1.001)
	15 trials	14 trials	21 trials	9 trials	15 trials
	p = 0.037	p<0.001	p<0.001	p<0.001	p<0.001
	I² = 76	I² = 100	I² = 100	I² = 100	I² = 100
$0.00–0.49			1.007
			(1.002, 1.012)
		0 trials	1 trial	0 trials	0 trials
$0.50–0.99					1.001
					(1.000, 1.001)
			0 trials	0 trials	1 trial
$1.00–1.99				1.003
				(0.998, 1.008)
				1 trial	0 trials
$2.00–4.99					1.001
					(1.001, 1.002)
					2 trials
					p = 0.099
					I² = 100
$5.00 +					1.000
					(1.000, 1.001)
					3 trials
					p = 0.112
					I² = 100