120 DOMESTICATED ANIMALS AND PLANTS 
that is variable, and where variability can be accurately meas- 
ured, will afford a problem in statistical determination. 
MILK AND FAT FROM 1200 Cows IN 
ILLINOIS DaAIRIEs ! 
Milk | Fat 
if ff i v t 
1,500 ife) i a5 2 
2,500 59 | 5 22 
3,500 178 12 173 
4,500 256 175 297 
53590 253 225 349 
6,500 209 ays 22 
7,500 Lie 325 7 
8,500 63 | 375 39 
9,500 28 ' 216 17 
10,500 10 475 4 
T1,500 2 | 525 I 
12,500 I 
1200 1200 
M=5515 M = 218.2 
o = 1770.1 c= 71.794 
C= 3254 C= 32.90 
The solution of the problem on milk and fat tells us that 
cows vary among themselves 1770 pounds of milk and over 71 
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 Illinois; 
data collected by Professor Fraser. 
