
❳⑩❈ ❙❯❻❚ ❚❍➮◆● ❑➊
❚!♥ ❚❤➜% ❚&
✣➔ ◆➤♥❣✱ ✷✵✶✾
❚!♥ ❚❤➜% ❚& ✶✴✼✼
❈❤"#♥❣ ✷✳ ❇✐➳♥ ♥❣➝✉ ♥❤✐➯♥
✶✳ ✣,♥❤ ♥❣❤➽❛
✲ ❍➔♠
X
①→❝ ✤(♥❤ +,➯♥ ❦❤/♥❣ ❣✐❛♥ ♠➝✉
Ω
✈➔ ♥❤➟♥ ❣✐→ +,( +,♦♥❣
R
✤89❝ ❣:✐ ❧➔ ❜✐➳♥ ♥❣➝✉
♥❤✐➯♥ ♥➳✉ ✈>✐ ♠:✐
x∈R
✱ +➟♣ ❤9♣ ❝→❝ ❦➳+ A✉↔
{ω:X(ω)< x}
❧➟♣ +❤➔♥❤ ♠C+ ❜✐➳♥ ❝D
♥❣➝✉ ♥❤✐➯♥✳
✲ ❚➟♣ ❤9♣ ❝→❝ ❣✐→ +,( ❝G❛
X
✤89❝ ❣:✐ ❧➔ ♠✐➲♥ ❣✐→ +,( ❝G❛
X
✱ ❦➼ ❤✐➺✉
X(Ω)
✳
✲ ◆L✐ ♠C+ ❝→❝❤ +,M❝ A✉❛♥✱ ❜✐➳♥ ♥❣➝✉ ♥❤✐➯♥ ❧➔ ♠C+ ✤↕✐ ❧89♥❣ ❝L +❤➸ ♥❤➟♥ ❣✐→ +,( ♥➔② ❤❛②
❣✐→ +,( ❦❤→❝ ♣❤Q +❤✉C❝ ✈➔♦ ❦➳+ A✉↔ ❝G❛ ♣❤➨♣ +❤S✳
❱➼ ❞3 ✶
✲ ●✐❡♦ ♥❣➝✉ ♥❤✐➯♥ ✸ ❧➛♥ ♠/0 ✤2♥❣ ①✉✳ ●5✐
X
❧➔ 78 ❧➛♥ ♠➦0 7➜♣ ①✉➜0 ❤✐➺♥✳ ❑❤✐ ✤>
X
❧➔
♠/0 ❜✐➳♥ ♥❣➝✉ ♥❤✐➯♥ ♥❤➟♥ ❝→❝ ❣✐→ 0DE ✵✱ ✶✱ ✷ ✈➔ ✸✳
✲ ●5✐
Y
❧➔ 78 ♥❣KL✐ ✤➳♥ ✤M ①➠♥❣ O ❝P❛ ❤➔♥❣ ❆❇ 0D♦♥❣ ♠/0 ♥❣➔②✳ ❑❤✐ ✤>
Y
❧➔ ❜✐➳♥ ♥❣➝✉
♥❤✐➯♥ ♥❤➟♥ ❝→❝ ❣✐→ 0DE ✵✱ ✶✱ ✷✱✳ ✳ ✳ ✳
✲ ●5✐
Z
❧➔ ❝❤✐➲✉ ❝❛♦ ❝V❛ ♠/0 ❤5❝ 7✐♥❤ ♣❤M 0❤W♥❣ ✭✤Y♥ ✈E✿ ❝♠✮✳ ❑❤✐ ✤>
Z
❧➔ ❜✐➳♥ ♥❣➝✉
♥❤✐➯♥ ♥❤➟♥ ❝→❝ ❣✐→ 0DE 0D♦♥❣ ❦❤♦↔♥❣
(0,+∞)
✳
❚!♥ ❚❤➜% ❚& ✷✴✼✼
4❤➙♥ ❧♦↕✐
✲ ❇◆◆ ,U✐ ,↕❝✿ ❇◆◆ ❝L +➟♣ ❣✐→ +,( ❝L WD ❧89♥❣ ❤X✉ ❤↕♥ ❤♦➦❝ ✈/ ❤↕♥ ✤➳♠ ✤89❝✳
✲ ❇◆◆ ❧✐➯♥ +Q❝✿ ❇◆◆ +❤Z❛ ❝→❝ ✤✐➲✉ ❦✐➺♥ W❛✉✿
✰ +➟♣ ❣✐→ +,( +↕♦ +❤➔♥❤ ✶ ✤♦↕♥✱ ❦❤♦↔♥❣ ❤♦➦❝ ❤9♣ ❝→❝ ✤♦↕♥✱ ❦❤♦↔♥❣✳
✰ ❱>✐ ♠:✐ ❝ +❛ ❝L
P(X=c) = 0
✳
❈❤➥♥❣ ❤↕♥ ` ❱➼ ❞Q ✶✱
X, Y
❧➔ ❝→❝ ❇◆◆ ,U✐ ,↕❝✱ ❝b♥
Z
❧➔ ❇◆◆ ❧✐➯♥ +Q❝✳
✷✳ ❍➔♠ ♣❤➙♥ ♣❤=✐
✣,♥❤ ♥❣❤➽❛✿
❍➔♠ WD +❤M❝
FX(x) = P(X < x), x ∈R
✤89❝ ❣:✐ ❧➔ ❤➔♠ ♣❤➙♥ ♣❤D✐ ❝G❛
❜✐➳♥ ♥❣➝✉ ♥❤✐➯♥
X
✳
◆❤➟♥ ①➨B✿
❍➔♠ ♣❤➙♥ ♣❤D✐
FX(x)
❝❤➼♥❤ ❧➔ ①→❝ W✉➜+
X
♥❤➟♥ ❣✐→ +,( +,♦♥❣ ❦❤♦↔♥❣
(−∞, x)
✳
❚!♥ ❚❤➜% ❚& ✸✴✼✼

❚➼♥❤ ❝❤➜&✿
✐✮
0≤FX(x)≤1,∀x∈R
✐✐✮
FX(x)
✤#♥ ✤✐➺✉ ❦❤)♥❣ ❣✐↔♠ ✈.✐ ♠/✐
x∈R
✐✐✐✮
FX(x)
❧✐➯♥ 23❝ 25→✐ ✈.✐ ♠/✐
x
✱ 28❝ ❧➔
lim
x→x−
0
FX(x) = FX(x0),∀x0∈R
✐✈✮
lim
x→+∞FX(x) = 1,lim
x→−∞ FX(x) = 0
◆❤➟♥ ①➨&✿
✐✮
P(X≥a) = 1 −F(a)
✐✐✮
P(a≤X < b) = F(b)−F(a)
❚!♥ ❚❤➜% ❚& ✹✴✼✼
❱➼ ❞. ✷
❈❤♦ ❜✐➳♥ ♥❣➝✉ ♥❤✐➯♥
X
❝, ❤➔♠ ♣❤➙♥ ♣❤1✐
F(x) = a+b. arctan x, x ∈R
❛✮ ❚➻♠
a
✈➔
b
✳
❜✮ ❚➻♠
x
8❛♦ ❝❤♦✿
P(X≥1−x) = 1/4
●✐↔✐✳
❛✳ ❚❛ ❝=✿
lim
x→+∞F(x) = 1
lim
x→−∞ F(x) = 0 ⇔(a+bπ
2= 1
a−bπ
2= 0 ⇔(a= 1/2
b= 1/π
❜✳
P(X≥1−x) = 1 −P(X < 1−x) = 1 −F(1 −x)
= 1 −1/2 + 1/π ∗arctan(1 −x)= 1/2−1/π ∗arctan(1 −x) = 1/4
✳
❚@ ✤=✿
arctan(1 −x) = π/4
❤❛②
x= 0
✳
❚!♥ ❚❤➜% ❚& ✺✴✼✼
❱➼ ❞. ✸
❈❤♦ ❜✐➳♥ ♥❣➝✉ ♥❤✐➯♥
X
❝, ❤➔♠ ♣❤➙♥ ♣❤1✐
F(x) =
0, x < 0
ax2+b, 0≤x < 2
1, x ≥2
❛✮ ❚➻♠
a
✈➔
b
✳
❜✮ ❚➻♠ ❤➔♠ ♣❤➙♥ ♣❤1✐ ❝:❛
Y= 2X+ 1
✳
●✐↔✐✳
❛✳ ❱➻
F(x)
❧✐➯♥ 23❝ 25→✐ ♥➯♥
lim
x→0−
F(x) = F(0)
lim
x→2−
F(x) = F(2) ⇔(0 = b
4a+b= 1 ⇔(a= 1/4
b= 0
❚!♥ ❚❤➜% ❚& ✻✴✼✼

❜✳ ❚❤❡♦ ✤'♥❤ ♥❣❤➽❛✿
FY(y) = P(Y < y) = P(2X+ 1 < y)
=P(X < (y−1)/2) = F((y−1)/2)
=
0,(y−1)/2<0
1/4∗[(y−1)/2]2,0≤(y−1)/2<2
1,(y−1)/2≥2
=
0, y < 1
1/16 ∗(y−1)2,1≤y < 5
1, y ≥5
❚!♥ ❚❤➜% ❚& ✼✴✼✼
✸✳ ❇✐➳♥ ♥❣➝✉ ♥❤✐➯♥ +,✐ +↕❝
❈❤♦
X
❧➔ ❜✐➳♥ ♥❣➝✉ ♥❤✐➯♥ 56✐ 5↕❝ ✈:✐ ;➟♣ ❣✐→ ;5'
X(Ω)
✳ ❑❤✐ ✤@✱ ❤➔♠
p(x) = (P(X=x), x ∈X(Ω),
0, x /∈X(Ω),
✤CD❝ ❣E✐ ❧➔ ❤➔♠ ❦❤G✐ ①→❝ I✉➜; ✭♣5♦❜❛❜✐❧✐;② ♠❛II ❢✉♥❝;✐♦♥✮✳
❚5♦♥❣ ;5C6♥❣ ❤D♣
X(Ω) = {x1, ..., xn}
❤O✉ ❤↕♥ ✈➔
pi=P(X=xi)
✱ ;❛ ❝@ ❜↔♥❣ ♣❤➙♥
♣❤G✐ ①→❝ I✉➜;✿
Xx1x2
✳✳✳
xn
P p1p2
✳✳✳
pn
◆❤➟♥ ①➨3✿
✐✮
Ppi= 1
✐✐✮ ❍➔♠ ♣❤➙♥ ♣❤G✐ ❝S❛
X
I➩ ❧➔
FX(x) = P(X < x) = X
xi<x
P(X=xi)
❚!♥ ❚❤➜% ❚& ✽✴✼✼
❱➼ ❞8 ✹
▼!" ❧$ %↔♥ ♣❤➞♠ ❝- ✶✷ %↔♥ ♣❤➞♠✱ "1♦♥❣ ✤- ❝- ✽ ❝❤➼♥❤ ♣❤➞♠ ✈➔ ✹ ♣❤➳ ♣❤➞♠✳ ▲➜② ♥❣➝✉
♥❤✐➯♥ ✷ %↔♥ ♣❤➞♠✳ ●D✐
X
❧➔ %E ❝❤➼♥❤ ♣❤➞♠ "1♦♥❣ ✷ %↔♥ ♣❤➞♠ ❧➜② 1❛✳ ❚➻♠ ♣❤➙♥ ♣❤E✐ ❝J❛
X
✱ ①→❝ ✤M♥❤ ❤➔♠ ♣❤➙♥ ♣❤E✐ ✈➔ "➼♥❤ ①→❝ %✉➜"
P(1 ≤X < 3)
✳
●✐↔✐✳
❚❛ ❝@
X
❧➔ ❜✐➳♥ ♥❣➝✉ ♥❤✐➯♥ 56✐ 5↕❝ ♥❤➟♥ ❝→❝ ❣✐→ ;5'✿ ✵✱ ✶✱ ✷✳
P(X= 0) = C2
4/C2
12 = 1/11
P(X= 1) = C1
8C1
4/C2
12 = 16/33
P(X= 2) = C2
8/C2
12 = 14/33
❇↔♥❣ ♣❤➙♥ ♣❤G✐ ①→❝ I✉➜;✿
X
✵ ✶ ✷
P
✶✴✶✶ ✶✻✴✸✸ ✶✹✴✸✸
❚!♥ ❚❤➜% ❚& ✾✴✼✼

X
P
FX(x) = P(X < x) = X
xi<x
P(X=xi)
=
0, x ≤0
1/11,0< x ≤1
1/11 + 16/33,1< x ≤2
1/11 + 16/33 + 14/33, x > 2
=
0, x ≤0
1/11,0< x ≤1
17/33,1< x ≤2
1, x > 2
P(1 ≤X < 3) = P(X= 1) + P(X= 2) = 16/33 + 14/33 = 10/11
X
X
X
Aii i = 1,2,3,4Ai
P(X= 1) = P(A1) = 0,7P(X= 2) = P(¯
A1A2) = 0,3∗0,7 = 0,21
P(X= 3) = P(¯
A1¯
A2A3) = 0,3∗0,3∗0,7 = 0,063
P(X= 4) = P(¯
A1¯
A2¯
A3) = 0,3∗0,3∗0,3 = 0,027
X
PFX(x) = P
xi<x
P(X=xi) =
0, x ≤1
0,7,1< x ≤2
0,91,2< x ≤3
0,973,3< x ≤4
1, x > 4

X
X
H1, H2{H1, H2}
X
P(X= 0) = P(H1)P(X= 0|H1) + P(H2)P(X= 0|H2)
= 2/10 ∗6/10 + 8/10 ∗7/10 = 0,68
P(X= 1) = P(H1)P(X= 1|H1) + P(H2)P(X= 1|H2)
= 2/10 ∗4/10 + 8/10 ∗3/10 = 0,32
X
P
X FX(x)f(x)
FX(x) =
x
Z
−∞
f(t)dt, x ∈R
f(x)X
f(x)≥0
+∞
R
−∞
f(x)dx = 1 f(x) = F′
X(x)
f(x)
P(X=c) = 0 c
P(a≤X≤b) = . . . =P(a < X < b) = FX(b)−FX(a) =
b
R
a
f(x)dx
f(x)FX(x) = Rx
−∞ f(t)dt

