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PDF of Lecture Notes - School of Mathematical Sciences

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2. STATISTICAL INFERENCE<br />

Figure 20: Relationships <strong>of</strong> the tests to the log-likelihood function<br />

Solve for θ 0 in W 2 ≤ z(α/2) 2 .<br />

Recall, W =<br />

√<br />

ni(ˆθ)(ˆθ − θ 0 )<br />

=⇒ ˆθ − √<br />

z(α/2)<br />

ni(ˆθ)<br />

≤<br />

θ 0 ≤ ˆθ + √<br />

z(α/2)<br />

ni(ˆθ)<br />

i.e., ˆθ ±<br />

z(α/2)<br />

√ .<br />

ni(ˆθ)<br />

Score Test<br />

Need to solve for θ 0 in V 2 =<br />

(<br />

U(θ 0 ; x)<br />

√<br />

ni(θ0 )) 2<br />

≤ z(α/2) 2 .<br />

LR Test<br />

Solve for θ 0 in 2(l(ˆθ; x) − l(θ 0 ; x)) ≤ χ 2 1,α = z(α/2) 2 .<br />

Example:<br />

X 1 , . . . , X n i.i.d. Po(λ).<br />

109

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