[理工] [機率] 一題條件機率

看板Grad-ProbAsk作者 (Daniel)時間15年前 (2010/08/02 15:32), 編輯推噓0(006)
留言6則, 2人參與, 最新討論串1/5 (看更多)
From families with three children,a family is selected at random and found to have a boy. What is the probability that the boy has (a)an older brother and a younger sister (b)an older brother (c)a brother and a sister? Assume that in a three-child family all gender distributions have equal probabilities. a小題答案是1/14 b小題是13/42 c小題是3/7 感謝幫忙回答的人 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 114.39.24.233 ※ 編輯: aj0938 來自: 114.39.24.233 (08/02 15:34)

08/03 15:21, , 1F
我算成一開始有8種可能,知道一個男生所以7/8,然後a有
08/03 15:21, 1F

08/03 15:22, , 2F
1種,bc各3種情形,結果是1/7 3/7 3/7 = =錯很大的樣子..
08/03 15:22, 2F

08/05 09:35, , 3F
我算的答案跟樓上一樣...
08/05 09:35, 3F

08/05 09:38, , 4F
第一題的我覺的很怪 因為樣本空間只有八種
08/05 09:38, 4F

08/05 09:39, , 5F
為什麼分母會出現14...="=(還是我誤解題意?)
08/05 09:39, 5F

08/05 10:00, , 6F
另外一種想法是1/12 5/12 6/12...也不同= 3=
08/05 10:00, 6F
文章代碼(AID): #1CLdHvzn (Grad-ProbAsk)
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文章代碼(AID): #1CLdHvzn (Grad-ProbAsk)