108 Relationship of Intelligence to Size and Shaj^e of Head 
If we pass to the quantitative measurement of these groups, we may compare 
them either (i) by equivalence of variability, or (ii) by equivalence of class. 
These two methods of approaching the matter are indicated in Tables I 
and II. 
If we take Ci the standard deviation of intelligence as unit, we obtain the three 
scales given in Table I, and we see that the scale differs somewhat for girls, boys, 
and men. 
TABLE I. 
Relative Scales of Intelligence with the Standard Deviation a; as Unit. 
Class 
School Girls School Boys 
Graduates 
Class 
Median Individual 
downwards 
Wlai DelOW top 01 
Slow Intelligent 
Group 
-113(7; below top of 
Slow Intelligent 
Group 
-046(7; above bottom 
of 3rd Class 
Median Individual 
downwards 
Median Individual 
upwards 
•8530-; above bottom 
of Slow Intelligent 
Group 
-733(7-iabove bottom 
of Slow Intelligent 
Group 
-436(7; below top of 
3rd Class 
Median Individual 
upwards 
Eange of Slow 
Intelligent 
•860o-i 
-846(7; 
1 From -046(7; 
> below median 
to 00 
Range of Pass 
Degrees 
Range of Slow 
•642o-i 
-722(7; 
Range of Slow Dull 
•640o-£ 
-725(7f 
Range of Very 
Dull 
From 2'135(ri below 
median to oo 
From 2-180(7; below 
median to oo 
Range of Intelligent 
1-033(7; 
l-108a-i 
(-482(7; 
1^'^"^^ 1-595(7; 
Range of 3rd Class 
Range of 2ud Class 
Range of Quick 
Intelligent 
From 1 •040o-j above 
median to oo 
From 1-221(7; above 
median to oo 
From 1031(7; above 
median to oo 
Range of 1st Class 
The divergence, however, is probably not wholly due to a difference of varia- 
bility. The bulk of the girls were observed by women-teachers, and of the boys 
by men-teachers, while the estimate of the graduates was formed in a wholly 
different manner, namely, by examination tests. Apart from this, women and 
men are not equally variable in any actually measurable character, and there is 
no reason to suppose they are necessarily so in intelligence. I have therefore 
rearranged the scales on the assumption that our common unit is the "Intelligent" 
group, and that this is the same for boys and girls and equal to the range of the 
