6. Multiple regression was performed on data obtained from 31 trees to predict usable volume from the height (in feet) and the diameter (in inches) of the tree. Partial computer results are shown below.

Predictor Coef SE Coef T Constant -57 . 988 8. 638 -6.71 Diameter 4. 7082 0. 2643 17 .82 Height 0. 3393 0. 1302 2.61 Analysis of Variance Source DF 5 5 Regression 2 7684. 2 Residual Error 28 421.9 Total 30 8106.1