TRANSFORMING BOTH SIDES OF A TREE

The volume of a tree trunk can be modeled as a cone or cylinder. Howev er, the variance of the observations increases with volume. To obtain variance homogeneity the response can be transformed, which, unfortuna tely, destroys the geometric relationship. In this article the method of transforming both sides of an equation is applied to model the Mini tab tree data and 70 observations on the volume of pine trees. In both examples the logarithmic transformation of both sides of the equation seems appropriate. To determine the effect of individual observations on this conclusion, the constructed variable for transforming both si des of the equation is derived. This variable is used to provide added variable plots for the transformation and in the construction of dele tion estimates of the transformation parameter and of the related t te st. The only statistical technique used is simple regression through t he origin. The article concludes with some comments on forest mensurat ion as a source of statistical problems.