a, = number of plots per stratum j
Pj = area proportion of stratum j of Ac
Yı3 = volume of plot i of stratum j (n3 plot)
T = number of strata
2 2
Estimate of variance: s^ = 2 P,s, ee em hir p Wine = VA)
j 2
n.
J [7 vs]
y Eur ATE MISERAT eM
2 2. Ti; n
Estimate of variance of stratum J S. =
j (n.- 1)
The two-stage unequal probability (PPS) sampling
M
> v
m à
j 3,
Estimate of total volume : ve —— 2x (m O40, Nu M Seu. (5)
J
in which M = number of primary units (PU) in the population on Ac
m = number of PU's in sample
v5 = volume of PU, 25)
x, = area of PU, (ha)
j J
and estimate of variance of total volume:
2 omm
; AN E:
Sy = - «s. (6)
t (m- cu
When all PU's are used, for total volume: ve = 2.9; . 1... 2 €)
and for variance (with a given weight) of total volume:
The tw
Estima
Plot v
which
b = re
Regres
Estima
Estima
in whi