I20 DOMESTICATED ANIMALS AND PLANTS 



that is variable, and where variabiUty can be accurately meas- 

 ured, will afford a problem in statistical determination. 



Milk and Fat from 1200 Cows in 

 Illinois Dairies ^ 



M = 55i5 

 a— 1770.1 

 C= 32.11 



M = 218.25 



<T= 71.794 



C= 32.90 



The solution of the problem on milk and fat tells us that 

 cows vary among themselves 1 770 pounds of milk and over 7 1 

 pounds of fat per year, but that the real variability of the two 

 characters is practically identical — 32.11 and 32.90. 



References. 1. " Principles of Breeding " (chap. xii). Davenport. 

 2. " Statistical Methods." C. B. Davenport. 



1 From the records of the dairy department of the University of IlHnois ; 

 data collected by Professor Fraser. 



