Quick...Coin toss
2013-02-08 9:09 am
I roll a fair coin 10 times. What is the probabity that I roll 5 heads given that I already roll 5 or 6 heads? How about the probability that I roll 6 heads given that I roll 5 or 6 heads?
回答 (1)
2013-02-08 7:41 pm
✔ 最佳答案
H : headT : tail
P(H) = 1/2
P(T) = 1/2
P(5H in 10 times)
= P(5H 5T)
= 10C5 x (1/2)⁵ x (1/2)⁵
= (10!/5!5!) x (1/2)⁵ x (1/2)⁵
= 252/1024
P(6H in 10 times)
= P(6H 4T)
= 10C6 x (1/2)⁶ x (1/2)⁴
= (10!/6!4!) x (1/2)⁶ x (1/2)⁴
= 210/1024
P(5H or 6H in 10 times)
= (252/1024) + (210/1024)
= 462/1024
The required probability
= P([6H in 10 times] | [5H or 6H in 10 times])
= P(6H in 10 time) / P(5H or 6H in 10 times)
= (210/1024) / (462/1024)
= 5/11
參考: fooks
收錄日期: 2021-04-13 19:17:56
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20130208000051KK00021