【#GRE留學(xué)外語考試# #2019年GRE數(shù)學(xué)考點：Conditional#】世上的事，只要肯用心去學(xué)，沒有一件是太晚的。你只要記住你的今天比昨天進步了一點，那么你離你的夢想也就更近了一步。©無憂考網(wǎng)整理了“2019年GRE數(shù)學(xué)考點：Conditional”，歡迎閱讀參考！更多相關(guān)訊息請關(guān)注©無憂考網(wǎng)！

　　Conditional

　　Probability of event A conditioned on the fact that event B has happened is
called the conditional probability and written as P(AIB).

　　P(AIB)=Probability Both A and B happens/ Probability B happens.

　　Example:

　　A six-sided die with faces from 1 to 6 is rolled twice. What is the
probability that the face 5 turned up on first try given that the sum of the two
faces is 9?

　　P(sum of faces is 9)=4/36=1/9.

　　P(face 5 turns up on the first try and sum is 9)=(1/6)*(1/6)=1/36.

　　P(face 5 turned up on first try given sum is 9)=(1/36)*(1/9)=1/4

　　Remember:

　　If P(AIB)=P(A),then two events A and B are independent, that is occurrence
of one does not influence the other