106 BUTTER-MAKING. 
The average test, according to the correct method, is 3.42%. 
It will be seen from the example quoted that there is a 
difference of more than .5%. If the percentage of fat or 
the number of pounds of milk is uniform, then it does not 
matter which of the two ways illustrated above is used. But 
as uniformity in either of these respects scarcely ever exists 
in practice, the only correct way of calculating the percentage 
is to find the total number of pounds of fat and divide it by 
the total number of pounds of milk; the result is .0342, which 
may be written 3.42%. 
J 70 
Fic. 63.—A Russian co-operative creamery in Siberia. 
(U. 8. Government Bulletin.) 
It is very common for creamery patrons to test the milk 
from each of their cows, then add the tests together and divide 
by the total number of cows tested. The result they will 
call the average test, and frequently such tests are made use 
of as evidence against a creamery operator to prove that his 
tests at the creamery were not correct. The fallacy is evident 
from what has been said above. 
