84 MODES OF RESEARCH IN GENETICS 



This fact is just now beginning to be recognized 

 by some experimentalists and hailed as a rather 

 original thought. It is not new. 



B. We may turn now to a wholly different 

 aspect of the statistical method, wherein it is 

 used for the purpose of predicting or estimating 

 the probable or the approximate condition in the 

 individual from a statistical examination of the 

 condition in the mass or the group. Resort is 

 had to the statistical method for this purpose 

 primarily in those cases where the outcome of 

 the event, or the condition of the thing, is deter- 

 mined by the combined action of a large number of 

 small causes, each about equally influential upon 

 the final result. 



Originally the statistical method was only 

 employed for this second purpose in cases where, 

 because of the multiplicity of the cause groups 

 involved in the determination of the event, and 

 the consequently small effect of each, it was 

 impossible to make any reasonable prediction re- 

 garding an individual from an examination of that 

 individual alone. Such employment might be 

 considered legitimate, though not very fruitful, 

 on the ground that prediction so made, uncertain 

 and doubtful as it may be, is after all perhaps 

 better than no prediction at all. As time has gone 

 on, however, there has been an increasing tendency 

 to assume that this use of the statistical method 

 had general a priori validity and could be profitably 



