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%. 



FIG. 63. A Russian co-operative creamery in Siberia. 

 (U. S. 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. 



