SIMPLERANDOMSAMPLE
SYSTEMATICSAMPLE
CLUSTERSAMPLE
SECONDARYDATA
PROBABILITY
STRATIFIED
STATISTICS
TECHNIQUE
ACCURATE
UNBIAS
CENSUS
ERROR
BIAS
POLL
U
X
S
F
S
T
R
A
T
I
F
I
E
D
M
U
E
I
E
T
U
K
O
Q
Y
E
E
A
C
C
U
R
A
T
E
U
B
S
U
A
I
P
S
R
E
C
L
U
S
T
E
R
S
A
M
P
L
E
K
T
O
E
C
J
F
J
P
O
X
E
R
R
O
R
H
K
K
X
Q
A
U
L
I
U
I
U
M
Z
G
A
D
W
W
S
K
J
E
Q
S
D
S
H
T
Y
I
G
A
X
V
U
A
L
L
Y
U
Q
I
K
H
Y
A
B
S
O
A
O
S
S
V
X
J
J
I
S
C
B
M
F
H
R
I
E
I
K
X
I
M
U
U
A
P
B
N
T
W
S
A
O
D
A
B
E
T
Y
M
I
O
X
I
V
R
T
A
E
E
A
S
O
I
D
N
D
A
L
X
U
D
I
I
Q
O
A
U
M
U
S
L
O
X
N
U
Y
T
K
M
M
N
W
K
C
B
Z
T
A
O
A
O
N
K
O
F
X
S
T
D
T
A
S
P
O
A
Y
Q
T
T
O
D
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I
C
G
D
B
P
E
E
R
A
F
L
B
C
J
I
U
L
W
S
V
E
W
E
W
N
D
C
E
I
G
Z
I
E
U
C
P
O
X
H
Y
S
S
I
S
K
D
H
L
B
U
T
L
N
A
S
O
C
A
P
I
V
A
I
L
A
U
N
P
Y
U
I
I
S
Y
A
I
E
I
B
M
E
H
U
F
M
Q
I
M
U
O
I
T
U
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M
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D
E
S
J
A
M
W
S
J
N
Q
I
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J
U
Y
S
A
P
P
J
M
A
K
U
U
L
F
S
M
U
S
J
O
L
O
O
A
L
P
P
S
G
M
J
Z
E
I
O
M
E
A
F
Q
I
E
A
E
E
T
P
E
O
A
V
