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Asymptotic Methods in Statistical Inference - Statistics Centre

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56<br />

• These considerations are often used to determ<strong>in</strong>e<br />

an appropriate sample size. Supposethat,<strong>in</strong>the<br />

preced<strong>in</strong>g example, we wish to atta<strong>in</strong> an asymptotic<br />

power of aga<strong>in</strong>st alternatives which are <br />

away from 0 . Thus we require<br />

Ã√ ( − <br />

= Φ<br />

0 )<br />

<br />

lead<strong>in</strong>g to<br />

− <br />

!<br />

= Φ ³ √ − ´<br />

<br />

µ − 2 <br />

≈<br />

<br />

<br />

E.g. for a level = 05 test, atta<strong>in</strong><strong>in</strong>g a power of<br />

= 9 aga<strong>in</strong>st = 5 requires<br />

≥<br />

i.e. ≥ 35.<br />

µ 1645 + 1282 2<br />

=3427<br />

5

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