XIV. Fraction Cull in International 1/4-ina'h Board Foot Volume Given the Tree Is 

 Unsound — Unforked and Forked Trees 



For fraction cull in International 1/4-inch board foot volume, the following model 

 was used: 



FCj = h^e I (33) 



where 



FCj = Predicted fraction cull in International 1/4-inch board foot volume given the 

 tree i^ unsound 



Yj = A function of the tree's attributes 



hj = A constant. 



This model differs from models (27) and (32) because (33) is asymptotic to instead of 

 1 and, therefore, it will allow predicted values of FC to exceed 1, which is just the 

 opposite from models (27) and (32) . This change in model form was by oversight rather 

 than design, even though it does not affect the legitimacy of the results. 



To fit model (33) , the following model was first fitted and screened using the same 

 basic procedures as in the cubic foot fraction cull equations: 



In(FC) = Y - (34) 



where 



FC = Actual fraction cull in International 1/4-inch board foot volume given the 

 tree is unsound 



Y = A function of the tree's attributes. 



This model was then transformed back to the form of model (33) and was found by least 

 squares regression through the origin to correct the model for possible log bias. The 

 models were tabulated and those that were reasonable and minimized RMSQR were picked. 

 All reasonable models examined for Engelmann spruce and for corkbark fir proved to be 

 much worse than the mean and, therefore, the models were dropped. 



To gain data strength, yellow pine and Douglas-fir were combined across all 

 National Forests (but not with each other) . 



XV. Fraction Cull in Scribner Board Foot Volume Given The Tree Is Unsound — Unforked 

 and Forked Trees 



The procedure and model forms used for fraction cull in Scribner board foot volume 

 were virtually the same as those used for fraction cull in International 1/4-inch board 

 foot volume. 



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