Re: [理工] 統計
※ 引述《mt1064 (AIG)》之銘言：
: Each game you play is a win with probability p. You plan to play 5 games,but
: if you win the fifth game then you will keep on playing until you lose.
: Find the excepted number of games that you lose.
: 這題有人知道怎麼做嗎?
令X為直至5次Win所需之次數 X~負二項(k=5,p)
令Y為直至lose所需次數Y Y~幾何(1-p)
E(X)=k/p=5/p E(Y)=1/(1-p)
令W=X+Y E(W)=E(X+Y)=E(X)+E(Y)=5/p+1/(1-p)=(5-4p)/[p(1-p)]
假如你的題意是在說"贏5次"之後開始玩,直到輸的話
那應該是這樣子
那如果有錯的話...希望高手幫我修正
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※ 發信站: 批踢踢實業坊(ptt.cc)
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