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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 211<br />

✬<br />

✫<br />

Primer: kvadrat normalno porazdeljene spremenljivke<br />

Naj bo X : N(0, 1) in Y = X 2 .<br />

Tedaj je FY (y) = P (Y < y) = P (X 2 < y) = 0 za y ≤ 0; in za y > 0<br />

FY (y) = P (|X| < √ y) = FX( √ y) − FX(− √ y)<br />

in ker/če je pX(x) soda funkcija<br />

pY (y) = pX( √ y) 1<br />

2 √ y + pX(− √ y) 1<br />

2 √ y<br />

Vstavimo ˇse standardizirano normalno porazdelitev<br />

pY (y) =<br />

⎧<br />

⎨<br />

⎩<br />

pa dobimo porazdelitev χ 2 (1).<br />

√1 1 y<br />

− y 2 − e 2 y > 0<br />

2π<br />

0 y ≤ 0<br />

= 1<br />

√ y pX( √ y)<br />

Univerza v Ljubljani ▲<br />

❙ ▲<br />

▲<br />

▲<br />

● ❙ ▲<br />

▲<br />

☛ ✖<br />

✩<br />

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