OF LOGICAL CLASS-FREQUENCIES, ETC. 
127 
together,” are not uncommon, but tire speaker seldom has any conception of the limits 
to (BC) actually implied by given values of (AB) and (AC). 
§ 33. To enforce the danger of rashly inferring, we take some figures from the 
illustrations of my previous memoir borrowed from the material of the Childhood 
Society. 
The following o 
re the proportions,"' 
per 10,000 
cases observed, of those with given 
defects and given 
comhinations of defects, for boy 
s and girls of all ages. 
A = development defects, B = 
nerve signs 
C = low nutrition, D = 
mental 
dulness. 
Boys. 
Girls. 
(U). 
. 10,000 
10,000 
(A). 
878 
G82 
(B). 
1,085 
850 
(C). 
285 
325 
(B). 
789 
G89 
(AB) .... 
29G 
248 
(AC) .... 
142 
180 
(AD) .... 
29G 
307 
(BC) .... 
134 
141 
(BD) .... 
455 
3G3 
(CD) .... 
123 
132 
(ABC) .... 
57 
GG 
(ABD) .... 
153 
128 
(ACD). . . . 
170 
80 
(BCD) .... 
G4 
G3 
(ABCD) . . . 
30 
33 
These figures give the following values for tire 
associationsf— 
Boys. 
Girls. 
jABl . . . 
0-750 
0-784 
■ lACl . . . 
0-848 
0 -9 I G 
! AD 1 ... 
0-84G 
0-900 
IBCl . . . 
0-783 
0-814 
1 BD1 . . . 
0-897 
0-905 
1 CD1 ... 
0-823 
0-835 
A hasty arguer might think he 
was safe in inferring from the values. 
e.g., ot 
1 BC 1 and } AC | 
that at least some 
A’s must 
be B, if not that A and 
B were 
* “ On the Association of Attributes in Statistics,” &c., ‘ Phil. Trans.,’ A, vol. 194. Table on p. 318, 
but the figures reduced to proportion per 10,000 cases observed, 
t Pages 306-307 of the same memoir. 
