The Measurement of Variation 51 



the true mean is probably somewhere between 15.5 -f .016 

 and 15.5 - .016 or 'between 15.516 and 15.484. The size 

 of the error is generally indicative of the number of the 

 individuals employed and the general dependability of the 

 work. 



Use of statistical methods. The use of statistical 

 methods enables the breeder to express quite accurately 

 the amount of variability which would otherwise be 

 expressed with considerable difficulty. It enables him 

 also to keep an accurate record of his work from year to 

 year and affords him a convenient method of comparing 

 one year's crop with another. 



It will be seen later that statistical methods may also be 

 employed to express correlation and extent of inherit- 

 ance. 



