P(A1) Ͱ A1 ͷେ͖͞Λද͢ → ֬ • ۭ֬ؒΛ໌Β͔ʹ͍ͯ͠ͳ͍ͱࠔΔ͜ͱ͕͋Δ • Ͳ͏͍͏ू߹্ʹ֬ΛೖΕΔͷʁ → σ ू߹ ଌ R ͔Β࣮ a, b Λબͼɼ۠ؒ I = [a, b], a, b ∈ [0, 1] Λߏ ͢Δɽ۠ؒ I ͷ “େ͖͞” ʹ͍ͭͯߟ͑Δɽ a b x M 16 / 42
P(A1) Ͱ A1 ͷେ͖͞Λද͢ → ֬ • ۭ֬ؒΛ໌Β͔ʹ͍ͯ͠ͳ͍ͱࠔΔ͜ͱ͕͋Δ • Ͳ͏͍͏ू߹্ʹ֬ΛೖΕΔͷʁ → σ ू߹ ଌ R ͔Β࣮ a, b Λબͼɼ۠ؒ I = [a, b], a, b ∈ [0, 1] Λߏ ͢Δɽ۠ؒ I ͷ “େ͖͞” ʹ͍ͭͯߟ͑Δɽ a b x M ϧϕʔάଌ L([a, b]) b − a 16 / 42
Conditional Probability C ∈ B, P(C) > 0 ͷͱ͖ɼ P(A|C) = P(A ∩ C) P(C) , A ∈ B Λࣄ C ͕༩͑ΒΕͨͱ͖ͷ A ∈ B ͷ͖݅֬ͱ͍ɼ P( · |C) Λ C ͕༩͑ΒΕͨͱ͖ͷ͖݅֬ଌͱ͍͏ɽ • ্هͷΑ͏ʹ͖݅֬Λఆٛ͢ΔͱɼP( · |C) (Ω, B) ্ͷ֬ଌʹͳ͍ͬͯΔ 17 / 42
B) ͕ಋೖ͞Εͨ • Γͷ֬ଌ P ʹରԠ͢Δͷͱͯ͠ɼؔ F Λಋೖ ͢Δ Distribution Function F : R → R ͕ ∀x ∈ R, F(x) = P(X ≤ x) = P ({ ω | X(ω) ≤ x }) ʹΑͬͯ F Λఆٛ͢Δͱ͖ɼF Λ X ͷྦྷੵؔ (cumu- lative distribution function; cdf) ͱ͍͏ɽ • P(X ≤ x) Λ X ≤ x ͱͳΔ֬ͱಡΈସ͑Δࣄ͕Ͱ͖Δ 23 / 42
: (Ω, B, P) ্ͷ r.v. ͱ͢Δɽ X ͕ D (Discrete) -type def ⇐⇒∃E ⊂ R (ߴʑՃࢉͳू߹) s.t. P(X ∈ E) = 1 Continuous type FX ɿX ͷؔͱ͢Δɽ X ͕ C (Continuous) -type def ⇐⇒∃fX : R → R+ (Մଌؔ) s.t. FX (x) = ∫ x −∞ fX (u) du, ∀x ∈ R 26 / 42
ΛɼX ͷ֬ີؔ (p.d.f.) ͱ͍͏ • fX(x) ≥ 0, ∫ ∞ −∞ f(u) du = 1, d dx FX(x) = f(x) ͕Γ ཱͭ • ࣮ࡍʹ֬ܭࢉΛ͢Δͱ͖ɼ P(a < x ≤ b) =F(b) − F(a) = ∫ b −∞ f(u) du − ∫ a −∞ f(u) du = ∫ b a f(u) du ͱ͢Δ 31 / 42
ͷ a, b ∈ R Λ༻͍ͯɼC-type ֬ม X ͷม Y = aX + b Λߟ͑Δɽ͜ͷͱ͖ɼY ͷ p.d.f. ΛٻΊΑɽ FY (y) = P(Y ≤ y) = P(aX+b ≤ y) = P ( X ≤ y − b a ) , a ≥ 0 P ( X > y − b a ) , a < 0 Ͱ͋Δ͔Βɼ FY (y) = FX ( y − b a ) , a ≥ 0 1 − FX ( y − b a ) , a < 0 34 / 42