172 



Testing Milk and Its Products. 



age of a number of single tests and the true average test 

 of the various lots. 



Methods of calculating average percentages. 



*56. 2X100 



=4.73 



149.8X100 



-=4.22 



1187 1187 



197. The figures given in the table show that when 

 the different lots of milk vary in test and weight, as in 

 the first case, the correct average test of the 1187 Ibs. 

 of milk is not found by dividing the sum of these tests 

 by five, which would give 4.14 per cent. ; but by divid- 

 ing 56.2 (the total amount of fat in the mixed milk) 

 by 1187 (the total amount of milk), which is 4.73; 

 this is the correct average test of the mixed milk made 

 up of the five different lots. 



In the second case, the variations in both the weights 

 of the different lots of milk and their tests, are com- 

 paratively small, and both methods of calculation give 

 therefore practically the same average test; but also in 

 this case, the correct average test is found by dividing 



