Geoscience Reference
In-Depth Information
For the
h
th stratum in Equation (3.6),
N
h
is the size of the stratum,
m
h
is the
number of nonempty units in the stratum, and
n
h
is the size of the initial
sample in the stratum; an unbiased variance estimator is
γ
∗
2
∑
(1
−π
π
)
hh
y
·
Var[
ˆ
]
τ=
.
(3.7)
2
h
h
=
1
Complete allocation stratified sampling compares well with nonadaptive
designs such as conventional stratified sampling and two-phase sampling and
realizes considerable improvements in sample efficiency (Brown et al., 2012).
The example provided by Brown (2011), shown in Figure 3.3, considers a
rare buttercup found in the South Island of New Zealand. The study area
was divided into 12 strata with 25 units in each. A simple random sample
2
3
5
2
2
21
1
1
1
3
2
3
1
1
1
1
6
7
13
1
2
28
3520
2
1
2
2
356
2
5
13
11
16
2
1
41
1
22
2
1
FIGURE 3.3
A population of Castle Hill buttercups. There are three hundred 100-m
2
quadrats with the
counts of buttercups shown. The study area is sectioned into 12 strata, and three quadrats are
sampled from each stratum.
