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Slika - Shrani.si

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A. Juriˇ<strong>si</strong>ć in V. Batagelj: Verjetnostni račun in statistika 620<br />

✬<br />

. . . Preizkuˇsanje regre<strong>si</strong>jskih koeficientov<br />

Teˇzje se je dokopati do cenilke za parameter σ 2 .<br />

Označimo Q 2 = n<br />

i=1 (Yi − A − BXi) 2 .<br />

Po nekaj računanja se izkaˇze, da velja E Q2<br />

= n − 2.<br />

σ2 Torej je S 2 = Q2<br />

n − 2<br />

= σ2<br />

n − 2<br />

Q 2<br />

σ 2 nepristranska cenilka za σ2 .<br />

S2 je neodvisna od A in B. Testni statistiki za A in B sta tedaj<br />

<br />

A − EA A − α<br />

TA = √ =<br />

DA S<br />

nC2 x<br />

<br />

n<br />

n i=1 X2 i<br />

TB =<br />

C2 A − α<br />

2 =<br />

x + nX S Cx<br />

B − EB<br />

√ DB =<br />

B − β<br />

S Cx,<br />

ki sta obe porazdeljeni po Studentu S(n − 2). Statistika za σ 2 pa je<br />

spremenljivka<br />

✫<br />

Q2<br />

= (n − 2)S2<br />

σ2 σ2 , ki je porazdeljena po χ2 (n − 2).<br />

Univerza v Ljubljani ▲<br />

❙ ▲<br />

▲<br />

● ❙ ▲<br />

▲<br />

☛ ✖<br />

▲<br />

,<br />

✩<br />

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