Table 3. Regression analysis of SF mediation model (standardized).

Predictive variables	Model 1		Model 2		Model 3
	β	t	β	t	β	t
Total number of donations	−0.277	−6.774***	0.156	3.722***	0.122	2.812***
SF					−0.123	−2.838**
R 2	0.076			0.024			0.038
F	45.899			13.859			11.045

Notes.

Model 1, Predicts the SF level based on the total number of donations; Model 2, Prediction of P1NP level based on the total number of donations; Model 3, Predicting P1NP level together with the total number of donations and SF level.

^*P < 0.05.

^**P < 0.01.

^***P < 0.001.