Association of State Foresters, and the Forest Service. 2 In many- 

 respects, particularly in office methods, these methods were in 

 fact the foundation on which the committee built its standardiza- 

 tion. The method followed in preparing the yield tables has 

 been elsewhere described in detail. 8 



APPLICATION OF VOLUME TABLES 



CORRECTION FOR LOCAL USE. 



Separate volume tables were not made for different sites in 

 the wide territory from Virginia to Texas, or for different form 

 classes. The following methods are suggested for testing the 

 applicability of the volume tables in any given locality, and for 

 making any corrections which appear from such tests to be 

 necessary. 



The dimensions of 20 to 25 felled trees in the locality are 

 measured after the manner employed in the construction of the 

 tables, care being taken to select these trees over a good range 

 of diameter 4 and height, and to observe the identical limits of 

 utilization shown in the tables for the unit concerned (cubic feet, 

 cords, or board feet by the International }£-inch rule, the Scrib- 

 ner rule, or the Doyle rule). The volumes of these trees are 

 computed by the standard methods, and the deviation of each 

 from the tabular volume of a tree of the same diameter and height 

 is then computed. It will be necessary to interpolate for tenths 

 of an inch in diameter and single feet in height in obtaining the 

 tabular volumes. The deviations are expressed as percentages 

 of the tabular volumes, and their average is compared with the 

 average deviation of the trees used in constructing the table, 

 which appears in the footnotes for each table. 



The total volume of the local trees is also compared with the 

 total of the tabular values, to obtain the aggregate difference. 

 The mere fact that this aggregate difference is small and com- 

 pares favorably with the aggregate difference used in construct- 

 ing the table (likewise given in the footnotes for each table) 

 does not prove anything, as Bruce 5 has pointed out; large 

 positive deviations among small trees may offset large negative 

 deviations among large trees, for example. But if the average 

 deviation of the local trees is not appreciably greater than that 

 of the table, and if their aggregate difference does not exceed 

 two and one-half times the average deviation of the table 

 divided by the square root of the number of trees used in the 



2 Committee on Standardization of Volume and Yield Tables, "methods 

 of preparing volume and yield tables. Jour. Forestry 24: 653-666. 1926. 



3 Bruce, D. a method of preparing timber-yield tables. Jour. Agr. Re- 

 search 32: 543-557, illus. 1926. 



* In checking the board-foot tables, no trees under 10 inches in diameter should be 

 used. 



a Bruce, D. a proposed standardization of the checking of volume tables. 

 Jour. Forestry, 18: 544-548, illus. 1920. 



3 



