推 goshfju:樹枝圖畫一下就出來了 07/18 12:17
An urn contains m white balls and n black balls. A ball is drawn at random
and its color noted. The ball is then replaced, along with p balls of the
same color. Finally s second ball is drawn at random. Which one is correct?
(1) P(2白)= m/(m+n)
(2) P(2黑)= P(1黑)
(3) P(1黑|2白)= (n+p)/(m+n+p)
(4) P(1白|2黑)= m/(m+n+p)
我的作法: http://ppt.cc/LdVZ
首先1跟2很明顯就不對了
然後3跟4是考貝式定理
如果按照我的樹狀圖用貝式定理乘來乘去的話實在是得不出選項的答案= =
但若舉個數字的例子答案應該就是4
請問一下若用純代數的話該怎麼解呢?
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