[商管] [數統] 幾題頗為艱難的題型

看板Grad-ProbAsk作者 (綠影)時間15年前 (2010/11/29 23:37), 編輯推噓2(204)
留言6則, 3人參與, 最新討論串1/1
1. Let X be a discrete random variable whose range is the nonnegative integers . Show that ∞ EX = Σ (1-Fx(k)) , where Fx(k) = P(X≦k) k=0 2. A random variable X is defined by Z = logX, where E(Z)=0 Is E(X) greater than ,less than , or equal to 1 ? 3. Does a distribution exist for which Mx(t)=t/(1-t),|t|<1, If yes ,find it ,if no ,prove it ? -- -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.116.96.51

11/29 23:46, , 1F
第一題觀念上可以寫幾項來看出,嚴謹的數學式要小技巧
11/29 23:46, 1F

11/29 23:48, , 2F
第二題隨便舉個例子好像是大於...
11/29 23:48, 2F

12/02 19:14, , 3F
第三題是不是卡方一
12/02 19:14, 3F

12/02 21:42, , 4F
第二題我以為是等於耶@@"
12/02 21:42, 4F

12/09 21:10, , 5F
第二題是大於等於 E(X)=E(e^Z)>=e^E(Z)=e^0=1
12/09 21:10, 5F

12/09 21:11, , 6F
根據Jensen's不等式
12/09 21:11, 6F
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