9\) 



VARIABILITY OF A SINGLE CHARACTER 



109 



Distribution as to 



Weight of Ears 



in Ounces 



number of other characters that can be measured, weighed, 

 counted, or in any other way accurately determined. Thus the 

 following is an actual distribution as to weight of ears, in which 

 the character is measured in terms of ounces instead of inches. 

 Here the problem deals with a different unit of value, so that 

 V now stands for ounces, while / stands for frequency, as be- 

 fore. The mode in this distribution is 9 

 ounces and the mean 8.807 ounces, the 

 derivation of which is left for the student 

 or reader by the methods already outlined. 



If now we should pick an ear that is 

 8.514 inches long and that weighs 8.807 

 ounces, it would be typical both as to 

 length and weight. _ So in the same way 

 other characters could be determined, 

 such as circumference, number of rows, 

 and in some cases even color, and any ear 

 that was "on the type " as to each char- 

 acter could be fairly called a typical ear. 



A typical individual is, therefore, one 

 that is typical, or average, as to all the 

 characters that are considered important. 

 Practical experience will show that there 

 are very few typical individuals in any 

 species, provided very many characters 

 are considered. 



Variability or deviation from type. But the average gives us 

 only partial information concerning the character we are studying. 

 It gives us no indication of the spread or range of the distribution, 

 jls to how many of the population have deviated from the type, or 

 how extensive was the deviation ; that is, the average gives us no 

 measure of variability, and it is such a measure that we now seek. 



Average deviation. Referring to the original distribution of 

 length of ears, let us consider how much each group of ears 

 deviates from the mean or average length, which is 8.514—. 



Mean 



.807 ounces. 



