536 
Miscellanea 
The equation to the surface of Q = 0'Q with normal marginal frequencies, for a total population 
of 1000, is : 
^0||(l + 3( P+? )-6^) 
where 
{(l+3(p+ ? ))«-48p3-}* 
p=£(l + a) for .r/o- x , 
q = $(l+a!) for 7//^, 
a having the usual significance attributed to it in Tables of the Probability Integral, e.g. 
Sheppard's. 
Diagram II. Isoplethes of Surface of Constant Association, Q — O'G. 
-i 1 r 
-2-0 
-1-0 ■ 
0Q 
1-0 
2-0 
Line of Means 
(y on x). 
Line of Modes 
(y on x) 
-2-0 -1-0 0 10 2'0 
Scale of xja x . 
The isoplethes are drawn for each tenth of the maximum value of z. 
