NATURE OF STATISTICAL KNOWLEDGE . 95 



a statistical prediction is made is essentially the 

 most sterile kind of knowledge that one can 

 possibly have so far as concerns the individual 

 event. It merely gives one the betting odds for 

 or against the occurrence of an event, and abso- 

 lutely nothing more. Now a wager, however 

 large, in the scientific sense neither discovers, 

 expounds, nor is a criterion of the truth. Bets, 

 in other word, are not evidence, though the 

 statistician sometimes seems to forget this, and 

 to deal with statistical ratios as though they had 

 probative worth in regard to phenomena. 



On the other hand, a prediction based on ex- 

 perimentally acquired knowledge of the deter- 

 minative cause of the individual event brings with 

 it a real knowledge of a natural phenomenon. 

 The predictions so made may not always turn 

 out correct, but when they do not, it incites us to 

 investigate the particular disturbing factor which 

 under such circumstances may overwhelm the 

 normally determinative cause of a particular 

 event. 



VI 



Man soil das Kind nicht mit dem Bade verschiitten. 

 The critical reader may be inclined to think that 

 this is exactly what the discussion in the preced- 

 ing sections has done. If, as has there been sug- 

 gested, that part of the statistical method which 

 uses the calculus of probability as a basis for the 



