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