Table 4.

Results for the quadratic effect of reward on online contribution (N=40,300).

Independent variablesa		Coefficientb	SEc	t40,290	P
Intercept		1.417	0.011	134.762	<.001
Main effects
	Psychological reward	0.261	0.008	34.581	<.001
	Material reward	0.688	0.009	78.670	<.001
Quadratic effects
	(Psychological reward)2	–0.015	0.001	–17.549	<.001
	(Material reward)2	–0.049	0.001	–49.246	<.001
Control variables
	Past online contribution	0.415	0.005	85.476	<.001
	Doctor review rating	0.189	0.006	32.996	<.001
	Clinic title	–0.099	0.010	–10.296	<.001
	Hospital level	–0.106	0.012	–9.228	<.001
	City level	–0.143	0.010	–13.941	<.001

^aModel summary: R²=.570, F_9,40,290=5935, P<.001.

^bStandardized regression coefficient.

^cSE: standard error.