16 
CIRCULAR 816, U. S. DEPARTMENT OF AGRICULTURE 
The data presented in this circular indicate that increased accuracy and 
some reduction in the cost of surveys could be realized by using, as the 
survey unit, a group of similar counties, instead of a single county; by 
varying the number of stops within a county or district, above a fixed 
minimum, according to population, as indicated by preliminary sampling; 
and by stratification of sampling to ensure representation of important 
environments. 
ft U.S. GOVERNMENT PRINTING OFFICE: 1949-837288 
LIBRARY OF CONGRESS 
0 000 889 301 9 
For sale by the Superintendent of Documents, U.S. Government Printing Office 
Washington 25, D.C.—Price 5 cents 
