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Asymptotic Methods in Statistical Inference - Statistics Centre

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31<br />

(why?) with ‘cumulant generat<strong>in</strong>g function’ (c.g.f.)<br />

à !<br />

<br />

log () = log √ <br />

= <br />

=<br />

∞X<br />

=1<br />

∞X<br />

=1<br />

<br />

!<br />

Ã<br />

√ <br />

! <br />

−( 2 −1)<br />

() <br />

!<br />

Thus has cumulants = −( 2 −1) (= 0 if<br />

=1and=1if = 2). Then (3.1) becomes<br />

() =<br />

⎡<br />

⎡<br />

⎣exp<br />

⎧<br />

⎨<br />

∞X<br />

⎩<br />

=3<br />

⎤<br />

−( 2 −1) ⎫<br />

⎬<br />

() ⎦ · ()<br />

! ⎭<br />

1+ 3<br />

⎢ 6 √ <br />

=<br />

()3 + 4<br />

24 ()4<br />

⎣<br />

+ 2 3<br />

72 ()6 + ³ −1´ ⎥<br />

⎦ · () (3.2)<br />

This gives the standard CLT: () → (), so<br />

<br />

→ Φ.<br />

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