I.—NOTATION AND TERMINOLOGY. 5 
whatever ; it merely excludes the other attributes noted in the 
particular investigation. Adjectives, as well as the symbols which 
may represent them, are naturally used in an inclusive sense, and 
care should therefore be taken, when classes are verbally described, 
that the description is complete, and states what, if anything, is 
excluded as well as what is included, in the same way as our 
notation. The terminology of the English census has not, in 
this respect, been quite clear. The “Blind” includes those who 
are ‘Blind and Dumb,” or “ Blind, Dumb, and Lunatic,” and so 
forth. But the heading “Blind and Dumb,” in the table relating 
to “combined infirmities,” is used in the sense “Blind and Dumb, 
but not Lunatic or Imbecile,” etc., and so on for the others. In 
the first table the headings are inclusive, in the second exclusive. 
REFERENCES. 
(1) Jevoxs, W, STANLEY, *‘On a General System of Numerically Definite 
Reasoning,” Memoirs of the Manchester Lit. and Phil. Soc., 1870. 
Reprinted in Pure Logic and other Minor Works; Macmillan, 1890. 
(The method used in these chapters is that of Jevons, with the notation 
slightly modified to that employed in the next three memoirs cited.) 
(2) Yur, G. U., “On the Association of Attributes in Statistics, ete.,” Phil. 
Trans. Roy. Soc., Series A, vol. cxciv., 1900, p. 257. 
(3) YULE, G. U., “On the Theory of Consistence of Logical Class-frequencies 
and its Geometrical Representation,” Phil. Trans. Roy. Soc., Series A, 
vol. exevii., 1901, p. 91. 
(4) Yur, G. U., “Notes on the Theory of Association of Attributes in 
Statistics,” Biometrika, vol. ii., 1903, p. 121. (The first three sections 
of (4) are an abstract of (2) and (3). The remarks made as regards the 
tabulation of class-frequencies at the end of (2) should be read in con- 
nection with the remarks made at the beginning of (3) and in this 
chapter : cf. footnote on p. 94 of (3). 
Material has been cited from, and reference made to the notation used in— 
(5) WARNER, F., and others, ‘ Report on the Scientific Study of the Mental and 
Physical Conditions of Childhood” ; published by the Committee, 
Parkes Museum, 1895. 
(6) WARNER, F., “Mental and Physical Conditions among Fifty Thousand 
Children, ete.,” Jour. Roy. Stat. Soc., vol. lix., 1896, p. 125. 
EXERCISES. 
1. (Figures from ref. (5).) The following are the numbers of boys observed 
with certain classes of defects amongst a number of school-children. 4, 
denotes development defects ; B, nerve signs; C, low nutrition. 
(4B0) 149 (a BO) 204 
(4ABy) 738 (aBy) 1,762 
(480) 225 (aBC) 171 
(4By) 1,196 (aBy) 21,842 
Find the frequencies of the positive classes. 
1: