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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 172<br />

✬<br />

✫<br />

Laplaceov intervalski obrazec<br />

Zanima nas, kolikˇsna je verjetnost Pn(k1, k2), da se v Bernoullijevem<br />

zaporedju neodvisnih poskusov v n zaporednih posku<strong>si</strong>h zgodi dogodek A<br />

vsaj k1–krat in manj kot k2–krat. Označimo<br />

xk =<br />

k − np<br />

√ npq<br />

in ∆xk = xk+1 − xk = 1<br />

√ npq .<br />

Tedaj je, če upoˇstevamo Laplaceov točkovni obrazec,<br />

Pn(k1, k2) =<br />

k2−1 <br />

k=k1<br />

Pn(k) = 1<br />

√ 2π<br />

k2−1 <br />

k=k1<br />

Za (zelo) velike n lahko vsoto zamenjamo z integralom<br />

Pn(k1, k2) ≈ 1<br />

√ 2π<br />

xk 2<br />

xk 1<br />

1 −<br />

e 2 x2<br />

dx.<br />

1 −<br />

e 2 x2k∆xk.<br />

Univerza v Ljubljani ▲<br />

❙ ▲<br />

▲<br />

● ❙ ▲<br />

▲<br />

☛ ✖<br />

▲<br />

✩<br />

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