1196. 
( or —^ = 1. 0288) this also leads to n 
According to fig. 1 for a relative cost 1 : 100, and r = 0. 6845 the proportion 
n n 
-& = 1 which approaches -E- = 1. 0288 as calculated above. 
n p n g 
The approximate value for 
n 
= 
n 
P 
c (1 - r 2 ) 
p 
c . r 
0. 053146 
4.6854 
0. 1065 
instead of 0.10288 as calculated above.. 
The total cost then equals only: 
't 
= 123 (10) + 1196 (0.1) 
= 1349. 6 US $. 
This means that for the given condition the same standard error (0. 5920 m /0. 05 ha) 
is obtained with C^. = 1350 instead of 1780 US $. 
It is interesting to compare this result with the one obtained from the application 
of an already existing volume table. 
In the above described example, crown cover was determined in 295 photo plots 
and field volume in 175 field plots, the latter forming a part of the former. A 
volume regression was calculated from the field and photo data from the 175 plots. 
As there is only one person doing all photo estimations, no adjustment of the mean 
photo volume necessary. In the example given below the volume regression 
already exists and in a number of new photo plots (n^ = 295) the crown cover is 
determined. The same equation is used as above. Substitution of c. = c 91 results 
— g 
in the same mean volume (Vg-^g) as calculated in case 1. 
The standard error of v 01r . gives the same result as calculated above: 
215 
s? 
V 
295 
6.27 
175 
= 0.5920 
+ 0. 2166" 
28.1403 
295 
and 
S- 
v 
0. 5920 m /0. 05 ha. 
295 
For the given conditions an adjustment of the mean plot volume (v 2 g 5 ) * s neces ‘ 
sary. Using for this purpose 60 plots which were originally used for the table 
construction, a slightly higher value for S- 
295(adj) 
results (STELLINGWERF, 1973-1).