N = 3 # broj primarnih jedinica

klasteri = list()
klasteri[[1]] = c(2, 4, 6, 5, 3, 1, 3, 4, 2, 5, 7, 4, 3)
klasteri[[2]] = c(3, 3, 4, 5, 5, 5, 6, 2, 5, 7, 6, 7, 8, 2, 4, 3)
klasteri[[3]] = c(1, 1, 2, 4, 2, 5, 7, 9, 6, 8, 9)
klasteri

n = 2
indeks = sample(1:N, n)
uzorak = klasteri[indeks]

# sume obelezja po klasterima
(ti = sapply(klasteri, sum))
(t_ocena = N * sum(ti[indeks]) / n)

# vrednost koju smo ocenjivali
(t = sum(ti))
# t = sum(c(klasteri[[1]], klasteri[[2]], klasteri[[3]]))

# disperzija ocene t_ocena
(D_t_ocena = N^2 * (1 - n/N) * sum((ti - t/N)^2) / (n * (N-1)))

# velicine klastera
(Mi = sapply(klasteri, function(x) {length(x)}))
(M_u = sum(Mi))

# kolicnicka ocena
(t_r = sum(ti[indeks]) * M_u / sum(Mi[indeks]))

R = sum(ti) / sum(Mi)
(D_t_r = N^2 * (1 - n/N) * sum((ti - R*Mi)^2) / (n * (N-1)))