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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 354<br />

✬<br />

✫<br />

. . . Učinkovitost cenilke<br />

Primer: Naj bo X : N(µ, σ). Če poznamo µ, je najučinkovitejˇsa cenilka<br />

za σ2 statistika S2 µ z disperzijo DS2 µ = 2σ4<br />

n . Popravljena vzorčna disperzija<br />

S2 pa je nepristranska cenilka istega parametra z disperzijo DS2 = 2σ4<br />

n−1 .<br />

Torej je učinkovitost S2 e(S 2 ) = DS2 µ<br />

=<br />

DS2 2σ 4<br />

n<br />

2σ 4<br />

n−1<br />

= n − 1<br />

n<br />

Iz tega vidimo, da e(S 2 ) → 1, ko n → ∞. Pravimo, da je cenilka S 2<br />

a<strong>si</strong>mptotično najučinkovitejˇsa cenilka za σ 2 .<br />

Univerza v Ljubljani ▲<br />

❙ ▲<br />

▲<br />

● ❙ ▲<br />

▲<br />

☛ ✖<br />

▲<br />

✩<br />

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