[問題] 問一題機率

看板Statistics作者rockken (態度)時間17年前 (2008/12/07 16:35)推噓0(0推 0噓 4→)

留言4則, 3人參與討論串3/3 (看更多)

There are three coins in a barrel. There coins, when flipped, will come up heads with respective probabilities 0.3,0.5,0.7. a coin is randomly selected from among these three and is then flipped sequentially. Let N_k be the number of heads obtained on the k flips. Find A) E(N_k) B) E(N_k |N_1=1) A)我有算出來 =0.5K 用雙重期望值 B)我算1/3(0.3*0.5(k-1)+0.5*0.5(k-1)+0.7*0.5(k-1)) 答案錯想法是想說第一次是正面所以只剩下k-1次，再去用bin(k-1,P) 有先設我用哪一個銅板。不知道大大可否幫我解惑，謝謝。 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 210.209.232.70 ※ 編輯: rockken 來自: 210.209.232.70 (12/07 16:45)

→

arbiteron

12/07 23:57, , 1^F

12/07 23:57, 1^F

→

ineihs

12/09 14:19, , 2^F

12/09 14:19, 2^F

→

rockken

12/09 15:09, , 3^F

12/09 15:09, 3^F