* THEORY OF STATISTICS. 
In calculating the coefficient of contingency (coefficient of mean square 
contingency) use the following groupings, so as to avoid small scattered fre- 
quencies at the extremities of the tables and also excessive arithmetic :— 
I. Group together (1) two top rows, (2) three bottom rows, (3) two first 
columns, (4) four last columns, leaving centre of table as it stands. 
II. Regroup by ten-year intervals (15-, 25-, 35-, ete.) for both husband and 
wife, making the last group ‘65 and over.” 
III. Regroup by 2-inch intervals, 585-605, etc., for father, 59:5-61°5, 
ete., for son. Ifa 3-inch grouping be used (585-615, ete., for both father and 
son), the coefficient of mean square contingency is0'465. [Both results cited 
from Pearson, ref. 1 of Chap. V.] 
IV. For cols., group 1+2, 3+4, . . . , 11412, 13 and upwards. Rows, 
0,1+2,3+4,..., 9+10, 11 and upwards. 
VI. For cols., group all up to 494'5 and all over 5215, leaving central cols. 
Rows singly up 20 : then 20-28, 28-44, 44-56, 56 upwards. 
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