94 
IOWA ACADEMY OF SCIENCE 
» n 
where (j = index of variability, or the amount the group as a whole varies from 
the mean, X = the amount of the deviation of any class] from the mean, and 
X = number of units in the class range. It is unity in all of these calculations. 
C = .IL.ioo% 
A 
where C = coefficient of variability. The 100% is to get the result into more 
convenient form, and is entirely arbitrary. 
E A = -t- . 6745 • 
“ V n 
where E A = the probable error of the mean. 
Eb=±-6745. ~ 
where E<j = the probable error of the index of variability. 
Tables 4, 5, and 6 show the constants as worked out for the vari- 
ous species and localities: 
TABLE No. 4. 
Constants For RudbecJcia hirta. 
Total 
Ames 
Center Point 
Hedrick 
n = 
3847 
558 
128 
3161 
A = 
11.3436 
11.8889 
11.5234 
11.2401 
D = 
2.4379 
2.0315 
2.0765 
2.5170 
C = 
21.4910% 
17.0877% 
18.0196% 
22.3933% 
Ea = 
.0265 
.0580 
.1238 
.0302 
e d = 
.0187 
.0410 
.0875 
.0214 
TABLE No. 5. 
Constants For Rudbeckia triloba . 
Ames 
n = 742 
A = 7.7345 
a = 1.2344 
C = 15.9590% 
E a = .0306 
E a = .0216 
TABLE No. 6. 
Constants For Helianthus grosse-serratus. 
Total 
n = 1296 
A = 14.1937 
O = 2.4864 
C = 17.5178% 
E a = .0466 
Ea= -0329 
Council Bluffs 
125 
13.9680 
1.8371 
13.1522% 
.1108 
.0784 
Ames 
1171 
14.2178 
2.5448 
17.8988% 
.0502 
.0355 
