72 The Opsonic Index — A Medico-Statistical Enqidrtj 
These are the distributions as they were worked out. By using a coarser 
grouping we obtain a more regular and more workable series as given in the 
following tables : — 
Normal Serum. 
Index 
Frequency 
Index 
Frequency 
Limits 
■70 
1 
1 ■06 
137 
•70= -695 to -755 
■76 
3 
V12 
53 
■82 
18 
1^18 
15 
■88 
48 
1-2^ 
2 
■9Jt 
140 
1^00 
193 
Total 
610 
Test Serum. 
Index 
Frequency 
Index 
Frequency 
Limits 
■28 
1 
1^00 
158 
•28 = -275 to -335 
■34 
0 
1^06 
135 
■40 
2 
1^12 
94 
\¥ 
1 
V18 
60 
1 
V24 
45 
■58 
5 
1-30 
25 
■64 
20 
1-36 
15 
■70 
22 
1-42 
9 
■76 
39 
V48 
4 
■82 
75 
V54 
4 
■88 
130 
V60 
6 
■94 
148 
V66 
I 
Total 
1000 
We may notice now some of the points of difference between the two distribu- 
tions. In the normal case the range of indices is between "70 and 1'24, whereas 
for test sera the range is much greater, being between •28 and 1"66. But whilst 
we may be prepared to admit that such indices as "70 and 1'24 are quite improb- 
able for normal sera, we still want to know the limits within which we are to 
diagnose a serum normal or abnormal. This point can to some extent be answered 
from the figures before us without further treatment. Thus, confining our atten- 
tion to the data for normal sera alone, we note that we may expect roughly 96 to 
97 of normal sera to afford indices ranging within the limits '89 and 1'19. So 
