R
the correlation coefficient, together with rsqr, are both measures of 
how well the regression model describes the data.

 R values near 1 indicate that the equation is a good description of 
the relation between the independent and dependent variables.  R equals 
0 when the values of the independent variables do not allow any 
prediction of the dependent variables, and equals 1 when you can 
perfectly predict the dependent variables from the independent variables.