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天才A 發表於 5-4-2011 12:05:35

conditional probability

諗左好耐都唔識..

已知b市 之天氣由上一天決定
假如 今天 下雨，明天下雨機會率為0.6
假如今天 不下雨，明天不下雨機會率為0.8

已知星期日 不下雨
求星期5下雨之機會率

應該係
P(星期五下雨丨星期日不下雨)
-------------------------------
    P(星期日不下雨)

分子易搞..
分母點搞??

-終場ソ使者- 發表於 5-4-2011 16:50:24

本帖最後由 -終場ソ使者- 於 5-4-2011 16:53 編輯

Use tree diagram,
the required probability=(0.2)(0.6)(0.6)(0.6)(0.6)+(0.2)(0.6)(0.6)(0.4)(0.2)+(0.2)(0.6)(0.4)(0.2)(0.6)+(0.2)(0.6)(0.4)(0.8)(0.2)+(0.2)(0.4)(0.2)(0.6)(0.6)+(0.2)(0.4)(0.2)(0.4)(0.2)+(0.2)(0.4)(0.8)(0.2)(0.6)+(0.2)(0.4)(0.8)(0.8)(0.2)+(0.8)(0.2)(0.6)(0.6)(0.6)+(0.8)(0.2)(0.6)(0.4)(0.2)+(0.8)(0.2)(0.4)(0.2)(0.6)+(0.8)(0.2)(0.4)(0.8)(0.2)+(0.8)(0.8)(0.2)(0.6)(0.6)+(0.8)(0.8)(0.2)(0.4)(0.2)+(0.8)(0.8)(0.8)(0.2)(0.6)+(0.8)(0.8)(0.8)(0.8)(0.2)=0.32992

天才A 發表於 6-4-2011 21:56:25

Use tree diagram,
the required probability=(0.2)(0.6)(0.6)(0.6)(0.6)+(0.2)(0.6)(0.6)(0.4)(0.2)+(0.2) ...
-終場ソ使者- 發表於 5-4-2011 16:50 http://nakuz.com/bbs/images/common/back.gif

=口=..
唔係無限loop落去既咩..
唔用sum of infinite 有可能得咩..

-終場ソ使者- 發表於 10-4-2011 17:00:28

你點樣想像到用無限有關呢?

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