84 Estimation of the General Intelligence of School Children 
the more reliable. Correcting for constant Form we get r] — *021 and r = — "209, 
Thus the correlation is either negligible or negative. The second alternative may 
be explained by the fact that a certain number of the duller boys remain longer 
at school because they are backward, and so reduce the average intelligence for the 
greater ages. 
Table V. Form and Intelligence. Taken as a contingency table the correlation 
is "547, which, corrected for age, becomes "454. The mean General Intelligence 
for different forms is : — 
Form 
Intelligence 
III 
11-3 
IV c 
11-4 
IV b 
11-1 
IV a 
11-2 
Yb 
ii -a 
Va 
12-2 
L. VI 
12-9 
VI 
14-8 
The rise in intelligence towards the end of the scale, which appears also in the 
high correlation is due to many of the duller boys not getting beyond form V b 
while only the sharpest ever reach the sixth form. 
Table VI. Age and Form. The correlation for this Table, found by the corre- 
lation ratio method is not so high as might be expected. This is on account of the 
admission of rather old boys to the lower forms, while those who join the school 
between the ages of 10 and 12 have generally reached one of the fifth forms 
or even the lower sixth by about the age of 14. 
The mean ages in the different forms are : — 
Form 
Age 
III 
11-9 
IV c 
12-7 
IV b 
13-1 
IVa 
13-4 
Yb 
13-7 
Va 
14-2 
L. VI 
14-8 
VI 
16-4 
Putting the above results together we have : — 
Intelligence and Examination Place, r ia = — '689 
r ls = -233(7?) 
= -044 (?■) 
= -130 (by fourfold table) 
r u = 0 
r, 3 = -343 ( v ) 
= -189 (by fourfold table) 
•547 
•602 
Age and Examination Place, 
Form and Examination Place, 
Age and Intelligence, 
Form and Intelligence, 
Age and Form, 
r 24 : 
'•34: 
Correlation of General Intelligence and Examination Place for constant Age 
and constant Form : — 
(a) With correlation ratio values of r 13 and r 23 p 12 = — - 867 + "012. 
(b) With smallest value of r 13 p 12 = - -825 ± -016. 
(c) With fourfold table values p 12 = - 817 + -017. 
