BIOMETRIC IDEAS AND METHODS 53 



true trend and significance. An example will 

 help to make the point here clear. Mortality 

 statistics are usually available only in units of 

 years of life. This is a rough unit. For actuarial 

 purposes it is desirable to know, for example, the 

 probable duration of life much more accurately 

 than in terms of years. It is possible to get this 

 information, accurate to a very high degree, by 

 the application of appropriate mathematical treat- 

 ment to the rough yearly data. In this connec- 

 tion, too, is to be considered the frequently made 

 statement that no statistical constant can be more 

 accurate than the data on which it is based. It is 

 very easy to demonstrate that this is not true. 1 



While, as has been pointed out in this section, 

 the methods and point of view of biometry have 

 not always been understood, yet the indications 

 are that matters are improving very rapidly in 

 this respect. In particular the great interest and 

 activity now being displayed in the study of in- 

 heritance and plant and animal breeding is doing 

 much to increase the use of biometric methods. 

 Breeders are accumulating masses of data which 

 they wish to analyze. To do this necessitates in 

 many cases the use of biometric methods. As 

 the really purposeful employment of these methods 

 to help solve practical problems increases they 

 must inevitably come to be better understood by 

 the great mass of biologists. 



1 Cf. Pearl, R. Amer. Nat., Vol. XLIII, pp. 238-240, 1909. 



