L 7/20
2.3.
Simple random sampling – three periods (2)
NON-STRATIFIED
STRATIFIED
Sample size calculation EN
First period
First period 2
n1þ2þ3 ¼
ðz×N1þ2þ3 ×σew1þ2þ3 Þ 2 ðTE – AEÞ
where
n1þ2þ3 ¼
ðz×N1þ2þ3 ×σew1þ2þ3 Þ 2 ðTE – AEÞ
2
where
N1 σ 2 þ N 2 σ 2 þ N3 σ 2 N1þ2þ3 e1 N1þ2þ3 e2 N1þ2þ3 e3
H1
σ2ew1þ2þ3 ¼ ∑i¼1
N1þ2þ3 ¼ N1 þ N2 þ N3 nt ¼
H2 N H3 N Nh1 2 σ þ ∑i¼1 h2 σ2h2 þ ∑i¼1 h3 σ2h3 N h1 N N
N1þ2þ3 ¼ N1 þ N2 þ N3
Nt n 1þ2þ3 N1þ2þ3
nht ¼
Second period
Nht n1þ2þ3 N1þ2þ3
Second period
Official Journal of the European Union
σ2ew1þ2þ3 ¼
2
n2þ3 ¼ where
ðz×N2þ3 ×σew2þ3 Þ 2 2 ðTE – AEÞ  – z2 ×N1 ×s2e1 n1
z2 ×N2þ3 ×σew2þ3
n2þ3 ¼
2
ðTE – AEÞ
– z2 ×
H1
∑h¼1
N2h1 2 :s nh1 eh1
!
σ2ew2þ3 ¼ N2 σ2e2 þ N3 σ2e3 N2þ3 N2þ3 N2þ3 ¼ N2 þ N3
(2) Simple Random Sampling may be applied with more than three sampling periods by relevant adjustments of the formulas.
H3
10.1.2023
nt ¼ Nt n2þ3 N2þ3
H2
σ2ew2þ3 ¼ ∑h¼1 ðNh2 :σ2eh2 Þ þ ∑h¼1 ðNh3 :σ2eh3 Þ