Il8 DOMESTICATED ANIMALS AND PLANTS 



Advantages of statistical studies. From the standpoint of 

 improvement, however, these methods give the breeder an 

 opportunity to study characters carefully, to know their average 

 value and the extent of their variability. Not only that, but 

 records kept from year to year will show the breeder what 

 progress, if any, he is making, and to what extent, if at all, the 

 animal or plant is responding to his selection. ^ 



Exercises. The student may well have much practice in solving distribu- 

 tions for mean, standard deviation, and coefficient of variability. Eight 

 actual distributions are appended, five in length and three in ounces, but 

 the student should have practice in taking his own measurements and in 

 making his own scheme and grouping. These different distributions arise 

 from different varieties or from different conditions of growth. 



M= 8.015 M= 7.141 

 <r= 1.348 <r= 1.267 

 C= 16.82 C= 17.74 



M= 8.322 M= 7.965 M= 7.063 

 (r=: 1.217 <'■= 1.018 (7= 1.070 

 C= 14-62 C= 12.78 0=15.15 



M= 7.901 M= 7.860 M= 8.807 

 <T= 2.657 <'■= 2592 «'■= 2-854 

 0=33.63 0=32.98 0=32.41 



1 " Principles of Breeding," pp. 434, 435. 



