[問題] 考古題不會寫求助消失

看板Statistics作者時間10年前 (2015/09/04 15:46), 10年前編輯推噓0(007)
留言7則, 2人參與, 最新討論串1/1
Let X1,X2...Xm be m indepedent random variables with values in N union { 0 } and with commom distribution P { X = k }= Pk, Define Rn = sum(Pk), k = n,...無窮 Show that E[min(X1,X2...,Xm)] = sum(Rn)^m, n = 1,2...無窮 解答寫: E[min(X1,X2...,Xm)] = sum(P{min(X1,X2,...,Xm)>=k}) 這是為什麼,看不出端倪求解版上大神們! -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 36.228.230.92 ※ 文章網址: https://www.ptt.cc/bbs/Statistics/M.1441352776.A.650.html

09/04 17:03, , 1F
sigma? summation?
09/04 17:03, 1F

09/04 17:06, , 2F
因為E(X) = sum_{all i} P(X=i)
09/04 17:06, 2F

09/04 17:07, , 3F
打太快 E(X) = sum_{all i} P(X > i)
09/04 17:07, 3F

09/04 17:10, , 4F
Note that X must be positive integer
09/04 17:10, 4F

09/04 17:13, , 5F
簡單的證明:http://tinyurl.com/m6aptuu
09/04 17:13, 5F

09/04 21:02, , 6F
神智不清都打錯了抱歉
09/04 21:02, 6F
※ 編輯: ccccccccc (36.228.230.92), 09/04/2015 21:05:22

09/04 21:07, , 7F
會了!謝謝您!
09/04 21:07, 7F
文章代碼(AID): #1LwKn8PG (Statistics)