Porter — The Growth of St. Louis Children. 285 
If p is allowed to represent one of the figures in the first 
column and A the average of all the measurements in a series, 
the figures opposite p in the second column will give the per 
cent. of individual measurements lying within the limits: 
A+p.dandA—p.d 
Suppose for example it were required to know how many 
of a series of 2192 girls aged 8 were of a height between the 
average (118.36 cm.) and a deviation of + 1.5 d (1.5. 3.7 
em. = 5.55 cm.), i. e. between 118.36 cm. + 5.55 cm. = 
123.91 cm. and 118.36 cm. — 5.55 ecm. = 112.81 cm. 
The number in the table opposite 1.5 is 68.8, which 
says that 68.8 per cent. of the 2192, or 1508, should fall 
within the limits stated. Then half this number must fall 
between A and A + 1.5 d (118.36 cm. and 123.91 cm.). In 
a similar manner it will be found that 50 per cent. of the 
whole number, or 1096, should fall within the limits A + d 
(118.36 cm. + 3.7 cm. = 122.06 cm. and 118.386 cm. — 3.7 
cm. = 116.51 em.), and 25 per cent. between A and A + d 
(118.36 cm. and 122.06 cm.). Thus may be calculated the 
number of observations which should occur at any deviation 
from the average. The theoretical and observed distribution 
of 2192 girls, aged 8, is compared in Table No. 7. 
