PDF of Lecture Notes - School of Mathematical Sciences
PDF of Lecture Notes - School of Mathematical Sciences
PDF of Lecture Notes - School of Mathematical Sciences
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1. DISTRIBUTION THEORY<br />
Solution. Observe that Z = h(X) = 1 σ X − µ σ ,<br />
( z +<br />
µ )<br />
σ<br />
⇒ f Z (z) = σf X 1<br />
= σf X (µ + σz)<br />
σ<br />
1<br />
= σ √ e (−1)<br />
2πσ<br />
2<br />
(2σ 2 ) (µ+σz−µ)2<br />
= 1 √<br />
2π<br />
e (−1)<br />
(2σ 2 ) σ2 z 2<br />
= 1 √<br />
2π<br />
e −z2 /2 = φ(z),<br />
i.e., Z ∼ N(0, 1).<br />
3. Suppose X ∼ Gamma (α, 1) and let Y = X λ , λ > 0.<br />
Find the <strong>PDF</strong> <strong>of</strong> Y .<br />
Solution. Since Y = 1 X, is a linear function, we have<br />
λ<br />
f Y (y) = λf X (λy)<br />
which is the Gamma(α, λ) <strong>PDF</strong>.<br />
= λ 1<br />
Γ(α) (λy)α−1 e −λy =<br />
λα<br />
Γ(α) yα−1 e −λy ,<br />
1.4 CDF transformation<br />
Suppose X is a continuous RV with CDF F X (x), which is increasing over the range <strong>of</strong><br />
X. If U = F X (x), then U ∼ U(0, 1).<br />
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