Re: [閒聊] 一題機率
看板Marginalman作者cuttlefish (無聊ing ><^> .o O)時間9年前 (2017/01/05 02:53)推噓21(21推 0噓 20→)留言41則, 11人參與討論串2/2 (看更多)
※ 引述《ILoveElsa (糸守町口嚼醬油釀造大師)》之銘言:
: 我覺得應該蠻簡單的
: 可是我腦袋打結ㄋ
: If 20 random numbers are selected independently from the interval (0,1), what
: is the approximate probability that the sum of these numbers is at least 8.
: 為什麼
: Var(Xi)=1/12
: 告訴窩
uniform distribution
1
E(Xi) = ∫ x dx = 1/2
0
1
E(Xi^2) = ∫ x^2 dx = 1/3
0
Var(Xi) = E(Xi^2) - [E(Xi)]^2 = 1/3 - 1/4 = 1/12
--
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