Комбинаторика

P(A/B)=P(A∩B)/P(B)

Formula yordamida topiladi,bundan P(A∩B)=P(B)*P(A/B).

Bu formula Ehtimolliklarni ko‘paytirish formulasi deyiladi.

P(A/B) ehtimollik shartli ehtimollik deyiladi.

• Misol:
• P(A)=1/2, P(B)=1/3,P(AUB)=p bo‘lsin.Agar A va B hodisalar:
• a)Birgalikda bo‘lmasa; b) bog‘liq bo‘lmasa p ni toping.
• Yechish.A va B hodisalar birgalikda bo‘lmasa P(A∩B)=0.Ammo
• P(A+B)=P(A)+P(B)-P(A∩B),bundan
• p=1/2+1/3-0=5/6
• b)A va B hodisalar o‘zaro bog‘liq bo‘lmasa,u holda
• P(A∩B)=P(A)P(B)=1/2*1/3=1/6,
• P(A+B)=P(A)+P(B)-P(A∩B)=1/2+1/3-1/6=5/6