48 



Plant-Breeding 



Average deviation = 



Standard deviation. The operations for finding the 

 standard deviation are the same as for the average devia- 

 tion except that the deviations in column D are squared 

 before multiplying by the frequency numbers (/), thus 

 giving the columns D 2 and D 2 f respectively. The sum 

 of the latter divided by the total number of individuals 

 and the square root of the result extracted gives the 

 standard deviation. This can be expressed by the follow- 

 ing formula : ^ r\if 



The details of determining the average and standard 

 deviation are as follows : 



