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# 機率-獨立事件

Q1:P(A or B)=0.6 and P(A)=0.2

問1：Find P(B) given that events A and B are mutually exclusive

問2：Find P(B) given that events A and B are independent

問1，求互斥事件我會求：

P(A or B)=P(A)+P(B)-P(A and B)

0.6=0.2+ P(B)-0

P(B)=0.4

我問題2有問題

問2：答案是0.5

獨立事件的公式：P(A or B)= P(A)+P(B)-P(A and B)

但我算出來不是0.5耶

請大大幫忙謝謝

### 1 Answer

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- myisland8132Lv 71 decade agoFavorite Answer
1 P(A or B)=P(A)+P(B)

0.6=0.2+P(B)

P(B)=0.4

2 P(A and B)=P(A)P(B)

P(A or B)=P(A)+P(B)-P(A)P(B)

0.6=0.2+P(B)-0.2P(B)

P(B)=0.5

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