probability of dice
2008-06-10 8:53 pm
a biased dice has 6 faces with numbers1,2,3,4,5,6. it is known that the probability of getting an odd number by throwing the dice once is 1/7.if each odd number has equal probability of appearing and each even number has equal probability of appearing,then the expected value of the number obtained by throwing the dice once is what?
回答 (2)
2008-06-11 2:08 am
✔ 最佳答案
一顆投擲結果不公平的骰子 投出奇數的機會相等 都是1/7 投出偶數的機會也相等 那麼投一次的期望值是多少?即是
P(1點) = P(3點) = P(5點) = 1/7
P(2點) = P(4點) = P(6點) = (1-1/7-1/7-1/7)/3 = (4/7) /3 =4/21
期望值 = value x probability
所以是
(1)(1/7) + (2)(4/21) + (3)(1/7) + (4)(4/21) + (5)(1/7) + (6)(21)
= 1/7 + 8/21 + 3/7 + 16/21 + 5/7 + 24/21
= (3+8+9+16+15+24)/ 21
= 75/21
= 25/7 or 3.57142857
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我只是解釋 分就畀上面啦
2008-06-10 18:09:13 補充：
001是錯的
002是對的
2008-06-10 9:10 pm
1/21*(1+3+5)+2/7*(2+4+6)=3.86
收錄日期: 2021-04-13 15:40:52
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080610000051KK00829