n 
0,000 
pied by 
ler 
py only 
sata 
om the 
le of 
he 
ch with 
ogether, 
ade of 
classes 
eech 
were 
| two-stage 
h cell 
| primary 
ing 
randomly 
ular and 
culation 
f ten 
different 
of à 
riation 
iot 
"ea 
jectare. 
ad 
plots 
on and 
n samples 
0 strata. 
ble 1. 
bed in 
obtained 
total M = 
62 PU's are present, 
with grid cells of 225 ha and two secondary units per primary unit. In 
all of which cover different areas. 
Sampling with PPS (probability proportional to size), using all 62 PU's 
(applying Formulae 7 and 8) and taking ten samples, gave means for total 
volume and standard deviation as indicated in Table 1. 
= 133, of which ng - 33 plots 
were respectively enumerated on the photos and on the ground. Crown cover 
percentage (c%) with intervals of 20 per cent were taken. Contrary to the 
other methods, only one sample was taken here, 
For the two-phase, 
calculated. 
or double sampling, 
The regression Y - b c, was calculated as: 
2 
The (standard error) 
the variance of b: 
The mean volume v 
m 
p 
and the total volume: 
The variance of the mean volume: 
2 
Sz 
V 
n 
p 
and the variance 
and 
For the total volume 
of estimate was 
9133 
S 
y-e 
Sb 
2.9694 (5.7617) 
= 17.109 n° /piot 
17.109 x 20 x 5917.9 = 
Y 
Il 
and so CVs could not be 
= 2.9694 c. 
3.9136 and 
0.0174. 
2,024,987 n° 
5.7616" (0.0174) + 2.9694? | 
0.8937 
0 
N 
u 
N 
I 
S 
v 
0.8937 (133) 
118.8660 
3 3 
10.90 m /plot (= 63.72% of 17.1090 m /plot). 
10.90 x 20 x 5917.9 
1,290,102 n° 
These results are also given in Table 1. 
Table 1 
Estimates of volume, 
the standard deviation for four sampling methods. 
  
  
  
  
  
  
  
4.7680 | 
133 
standard deviation and coefficient of 
Mean total Mean Coefficient 
Method volume standard deviation of variation Weiglit 
of s 
[^ CVs 
(m*) m % % 
Unrestricted 2,019,180 748,767.1 37.08 11.03 10 
Stratified 2,030,184 568,018.6 | 27.98 9.95 10 
Two-stage (PPS) | 1,892,441 509,727.9 26.93 8.45 10 
Two-phase 2,024,987 1,290,102.2 63.72 - 1 
  
  
variation of