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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 132<br />

✬<br />

✫<br />

. . . Pogojna verjetnost<br />

Primer: Iz posode, v kateri imamo 8 belih in 2 rdeči krogli,<br />

2× na slepo izberemo po eno kroglo. Kolikˇsna je verjetnost dogodka,<br />

da je prva krogla bela (B1) in druga rdeča (R2).<br />

1. Če po prvem izbiranju izvlečeno kroglo ne vrnemo v posodo<br />

(odvisnost), je:<br />

P (B1 ∩ R2) = P (B1) · P (R2/B1) =<br />

= 8<br />

10<br />

· 2<br />

9<br />

= 0, 18.<br />

2. Če po prvem izbiranju izvlečeno kroglo vrnemo v posodo<br />

(neodvisnost), je:<br />

P (B1 ∩ R2) = P (B1) · P (R2/B1) =<br />

= P (B1) · P (R2) = 8<br />

10<br />

· 2<br />

10<br />

= 0, 16.<br />

Univerza v Ljubljani ▲<br />

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