6 BULLETIN S39j U. S. DEPAETaIENTT OF AGRICULTURE. 
PERSONAL EQUATION VAMATION. 
COEXTLXG THE SAME SLIDES OX DLTTEBEXT DATS BY ONE ANALYST. 
Table 1 gives actual data obtained from counts made by each of 
two analysts working upon three slides which were prepared from the 
same bulk sample and upon which they made two counts on each of 
three successive days. 
Table 1. — Results of counts of same slides by tiro analysts on different days. 
Pate. 
Slide. 
Analyst. 
Count 
No. 
Bran 
particles. 
Hairs. 
Total. 
1918. 
Jan. 7 i 
A 
B 
B 
C 
2 
A 
B 
B 
c 
c 
A 
S 
! 
I 
B 
8 
1 
B 
B 
c 
I 
B 
B 
C 
c 
Keenan 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
2 
1 
: 
l 
2 
1 
2 
1 
2 
1 
2 
87 
92 
60 
60 
87 
SI 
103 
114 
B 
SO 
90 
87 
1 
82 
60 
49 
62 
64 
100 
96 
85 
77 
89 
83 
80 
S3 
- 
60 
77 
104 
106 
78 
77 
86 
So 
59 
64 
60 
:'S 
: 
74 
58 
"- 
64 
58 
62 
'' 
66 
55 
48 
66 
68 
54 
56 
52 
55 
65 
65 
66 
61 
! ' 
66 
71 
54 
55 
55 
55 
65 
62 
146 
Do.. 
Do.. 
do 
do 
156 
120 
Do. J 
do 
118 
Do.. 
do 
149 
Do.. 
do 
155 
Do.. 
Lvons 
161 
Do.. 
../..do 
166 
Do.. 
do 
150 
Do.. 
do 
138 
Do.. 
do 
152 
Do.. 
do 
144 
Jan. S 1 
Keenan 
142 
Do.J 
do _ 
151 
Do.. 
do 
115 
Do.. 
do 
97 
Do.. 
do 
" ^v 
Do. J 
do 
132 
Do.. 
Lvons 
154 
Do.. 
Do.. 
.....do 
do 
152 
137 
Do..; 
do 
132 
Do.. 
do 
154 
Do.. 
do 
142 
Jan. 9 1 
Keenan 
145 
Do.. 1 
do 
149 
Do..| 
do.. 
110 
Do.J 
do 
110 
.Do.. 
Do.. 
do 
do 
126 
148 
Do.. 1 
I r * 
Do.. 
do 
161 
Do..' 
do 
133 
Do.. 
do 
132 
Do.J 
do 
151 
Do.. 
do 
148 
For the purpose of emphasizing certain salient points, the results 
recorded in Table 1 have been rearranged in Table 2. in considering 
which it is necessary to regard the different portions carefully. 
Keenan's greatest variation in two counts of bran particles on a 
given slide on any one day was 17 points (slide C. Jan. 9. 1918), 
while Lyons' greatest variation was 11 points (slide A, Jan. 7. 1918). 
In the matter of counting hairs the greatest variation in the counts 
obtained on a given slide on any one day by Keenan was 12 points 
(slide C, Jan. 7, 1918), while Lyons' greatest similar variation was 6 
(in several instances). In these cases it appears therefore that the 
personal variation clue to the error of counting probably would not 
exceed 17 points in the case of particles or 1*2 points in the case of 
hairs. 
