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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 244<br />

✬<br />

✫<br />

Viˇsji momenti<br />

Viˇsji momenti so posploˇ<strong>si</strong>tev pojmov matematičnega upanja in disperzije.<br />

Moment reda k ∈ N glede na točko a ∈ R imenujemo količino<br />

mk(a) = E((X − a) k ).<br />

Moment obstaja, če obstaja matematično upanje E(|X − a| k ) < ∞.<br />

Za a = 0 dobimo začetni moment zk = mk(0);<br />

za a = EX pa centralni moment mk = mk(EX).<br />

Primera: EX = z1 in DX = m2.<br />

Če obstaja moment mn(a), potem obstajajo tudi v<strong>si</strong> momenti mk(a) za<br />

k < n.<br />

Če obstaja moment zn, obstaja tudi moment mn(a) za vse a ∈ R.<br />

mn(a) = E((X − a) n ) =<br />

n<br />

k=0<br />

<br />

n<br />

(−a)<br />

k<br />

n−k zk.<br />

Univerza v Ljubljani ▲<br />

❙ ▲<br />

▲<br />

● ❙ ▲<br />

▲<br />

☛ ✖<br />

▲<br />

✩<br />

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