CONDORCET. 403 



If '2 11 99 



54r^Ioo + ^^10o|'^^^*^^5400- 



I-Ience according to Condorcet's own words the lovohahilite p^opre 



1 99 .54 



should be — — - -h- . , that is — . But he himself says that the 



prohaUlite projjve is —r^, so that he takes ^-ttt -^ \ ^'^^ + tttt, 



lo3 100 [o400 lOOJ 



1 99 



and not — -r -^ ^'. .. ,. . That is, as is so frequently the case with 

 100 o400 ^ *^ 



Condorcet, his own words do not express his own meaning. 



Again sujDpose that there are ten cards and it is asserted that a 

 specified card has been drawn thrice running ; we proceed to esti- 

 mate the prohahilite propre of the event. Here the mean proba- 

 bility of all the other events is 



6 ^^ 3 9 ) , , . 999 



120 X ~~ + 90 X — -r + ——A , that is 



219 Y ^ ^ 1000 1000 ^ lOOOJ ' 219000 ' 



219 



Condorcet says that the jyrohabilite propre is , so that he 



1 I 999 1 \ ■ 



1000 • 1219000 "^ lOOOJ • 



741. Condorcet now proceeds to apply these results in the 

 following words : 



Ainsi siipposons, par exemple, que la probabilite du temoignage soit 



99 

 r— -, c'est-a-dire, que le temoin ne se trompe ou ne veuille tromper 



qu'une fois sur cent, on aura, d'apres son temoignage, la probabilite 



99 9900 , \. . . 1^. • ^ 1 T T.-rf' ^^^^ 



IT— ^ OU qu on a tire une carte determmee ; la probabilite 



^ .... , 9540 

 qu'on a tire deux fois la meme carte ; et la probabilite n-Q7rQ?| <1^^ on 



I'a tiree trois fois. 



We find some difficulties in these numbers. 

 Let p denote the prohahilite propre and t the probability of 

 the testimony ; then the formula to be applied is, we presume, 



^ In the first case it seems that Condorcet 



i^^+(i-p)(i-0' 



26—2 



