Table 3. Linear regression model of natural logarithm of annual incidence of HFRS and related factors in cities of Hebei province from 1999 to 2011.

Regression equation	R	R2	F value	P value	Durbin-Watson
y = −1.501+0.229X1+0.146X2	0.780	0.608	78.252	0.000	1.668
y = −0.668+0.188X1+0.127X2−0.054X3	0.803	0.644	25.936	0.000	1.839