428 



TRANSMISSION 



/ I> 



i x 5.83 



x 5.33 



1 x 4-83 

 o x 4-33 



2 x 3.83 



3 x 3-33 



9 x 2.83 

 8 x 2.33 



12 X 1.83 



19 x 1.33 

 32 x 0.83 

 40 x 0.33 

 67 x 0.17 

 63 x 0.67 

 38 x 1.17 



21 X 1.67 



8 x 2.17 



2 X 2.67 



_}_ x 3- J 7 

 3 2 7 



Df 



= 5.83 

 = 0.00 



= 4.83 



= o.oo 



= 7.66 



= 9-99 

 = 25-47 

 = 18.64 

 = 21.96 

 = 25.27 

 = 26.56 

 = 13.20 



= "-39 

 = 42.21 

 = 44.46 

 = 35-7 

 = !7-3 6 

 = 5-34 



=_JLLZ- 

 318.41 



The result of this calculation is that the 

 total deviation of 327 ears from their average 

 length is 318.41 inches, some above and some 

 below the mean. If now we divide 318.41 by 

 327, the number of ears involved, we have 

 0.97+ inches, which is a good expression of 

 the average deviation of this particular popu- 

 lation. If another variety should give a larger 

 quotient, we should conclude it to be more 

 variable. In this manner we may reduce the 

 variability of a whole population to a single 

 expression. 



Standard deviation. Mathematicians have 

 another method of calculating variability. It 

 differs from the one just discussed in only one 

 detail ; namely, the deviations are squared 

 before multiplication by their respective fre- 

 quencies, as in the table which follows : 



* The column marked /** is secured by squaring the various deviations, thus 

 eliminating the minus sign. For example, 5.83 X 5.83 = 33.9889. 



t The column marked D^f is obtained by multiplying the squared deviations 

 each by its respective frequency. For example, 8.0089 x 9 72.0801. 



\ The Greek capital sigma (2) is the usual sign of summation in mathematics. 



