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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 344<br />

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Srednja kvadratična napaka<br />

Vča<strong>si</strong>h je celo bolje vzeti pristransko cenilko z manjˇso disperzijo, kot jo<br />

ima druga, <strong>si</strong>cer nepristranska, cenilka z veliko disperzijo.<br />

Mera učinkovitosti cenilk parametra ζ je srednja kvadratična napaka<br />

Ker velja<br />

q(C) = E(C − ζ) 2<br />

q(C) = E(C − EC + EC − ζ) 2 = E(C − EC) 2 + (EC − ζ) 2<br />

jo lahko zapiˇsemo tudi v obliki<br />

q(C) = DC + B(C) 2<br />

Za nepristranske cenilke je B(C) = 0 in zato q(C) = DC.<br />

Če pa je disperzija cenilke skoraj 0, je q(C) ≈ B(C) 2 .<br />

Univerza v Ljubljani ▲<br />

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☛ ✖<br />

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