92 MODES OF RESEARCH IN GENETICS 



cussion, which essays to predict the probable 

 condition of the individual from the knowledge 

 of the mass, seems to furnish information about 

 causes. It wears a specious air of bringing a 

 kind of knowledge which in reality it not only 

 never does, but from the very nature of the case 

 never can furnish. 



Let us consider now a little more in detail the 

 nature of the prediction of the probable condition 

 of the individual from a knowledge of the mass or 

 group. It has been shown in an earlier section 

 (p. 83) that statistics give perfectly definite and 

 precise, and often very useful knowledge about 

 masses or groups. We are now, however, not 

 concerned with this as group knowledge, but 

 rather with one use to which such knowledge has 

 been put. This use is that which is comprised 

 in the subject of statistical probabilities, and 

 which involves the drawing of conclusions as to 

 the probable condition of the individual, based on 

 an exact knowledge of the mass. 



'In order to approach the subject in the simplest 

 way let us consider a concrete case. Suppose a 

 problem of the following sort were to be set before 

 us for answer : What is the probability that, 

 at some chosen moment of time, the next birth to 

 occur in, let us say, the city of Baltimore, will be 

 of a white child. Now if we look at this as a 



