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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 239<br />

✬<br />

✫<br />

Pogojno matematično upanje zvezne spremenljivke<br />

Zvezna slučajna spremenljivka X ima pri pogoju Y = y ima<br />

pogojno verjetnostno gostoto p(x|y) = p(x, y)/pY (y), x ∈ R<br />

in potemtakem pogojno matematično upanje<br />

E(X|y) =<br />

∞<br />

−∞<br />

xp(x|y) dx = 1<br />

pY (y)<br />

∞<br />

−∞<br />

xp(x, y) dx.<br />

Slučajna spremenljivka E(X|Y ) z gostoto pY (y) ima enako matematično<br />

upanje kot spremenljivka X<br />

E(E(X|Y )) =<br />

∞<br />

−∞<br />

E(X|y)pY (y) dy =<br />

=<br />

∞<br />

−∞<br />

∞<br />

−∞<br />

xpX(x)dx = EX.<br />

∞<br />

−∞<br />

Univerza v Ljubljani ▲<br />

❙ ▲<br />

▲<br />

xp(x, y) dx dy<br />

● ❙ ▲<br />

▲<br />

☛ ✖<br />

▲<br />

✩<br />

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