It is beneficial to be able to estimate the yield of useful product of a tree based on measurements of the tree taken before it is harvested. Measurements on four such variables were taken on a sample of trees, which subsequently was harvested and the actual weight of product determined. The variables are:

The first two variables (DBH and HEIGHT) are logically the most important and are also the easiest to measure. The data are given in Table 8.26. 

DBH: diameter at breast height (about 4 ft from ground level), in inches, HEIGHT: height of tree, in feet, AGE: age of tree, in years, GRAV: specific gravity of the wood, and WEIGHT: the harvested weight of the tree (in lb).