No. 599] ADVANCED REGISTRY COWS 679 



pounds of milk required by the Holstein-Friesian Asso- 

 ciation, must be calculated from the pounds of fat re- 

 quired. This was done by taking the average per cent, 

 of the whole population and calculating the number of 



pounds of milk, having the average per cent, that would 

 be necessary to make the required number of pounds of 

 fat. The reason for using the average per cent, of fat 

 of the whole population as a basis for calculating the 

 Holstein-Friesian Association requirement curve was 

 that since the correlation coefficient between age and per 

 cent, of fat was so small in a table shown subsequently 

 for another population, and since the popular concept is 

 that per cent, of fat is not influenced by age, we felt justi- 

 fied in using it. Attention is called to Table V, which 

 does not bear out this assumption entirely. For milk and 

 fat requirement, however, there is a strong correlation to 

 age, so the classes were considered separately, each class 

 having its own mean and deviation. Curves 2, 3, and 4 

 were based on these class means and deviations. Curve 



