一个可能的完备事件组

先把题目列出: 一共有10个硬币 , 依次投掷完 , 循环10次 , 如果出现3个硬币连续正面或反面 , 你输1元钱;否则 , 我输3元钱 。 你赌不赌?为什么? 解题如下: 1、设总概率为 P; 2、完成一次循环出现 3 个硬币连续正面的事件为 F; 3、完成一次循环出现 3 个硬币连续反面的事件为 B; 4、各次循环事件记为 A0...A9; 5、由于各循环次所用概率值唯一 , 可设为 P(A); 则有: P(A) = P(F + B)= P(F) + P(B) - P(F) * P(B)=P(B) + (1 – P(F)) * P(B); P = P(A0 + A1 + ... + A9); 为计算P值方便 , 再设: (1)T8 = P(A8 + A9) = P(A) + P(A) - P(A) * P(A) = P(A) + (1 - P(A)) * P(A) = P(A) + P(A’)*P(A); (2)T7 = P(A7 + T8) = P(A) + P(T8) - P(A) * P(T8) = P(A) + (1 - P(A)) * P(T8) = P(A) + P(A’)*P(T8); (3)T6 = P(A6 + T7) = P(A) + P(T7) - P(A) * P(T7) = P(A) + (1 - P(A)) * P(T7) = P(A) + P(A’)*P(T7); (4)T5 = P(A5 + T6) = P(A) + P(T6) - P(A) * P(T6) = P(A) + (1 - P(A)) * P(T6) = P(A) + P(A’)*P(T6); (5)T4 = P(A4 + T5) = P(A) + P(T5) - P(A) * P(T5) = P(A) + (1 - P(A)) * P(T5) = P(A) + P(A’)*P(T5); (6)T3 = P(A3 + T4) = P(A) + P(T4) - P(A) * P(T4) = P(A) + (1 - P(A)) * P(T4) = P(A) + P(A’)*P(T4); (7)T2 = P(A2 + T3) = P(A) + P(T3) - P(A) * P(T3) = P(A) + (1 - P(A)) * P(T3) = P(A) + P(A’)*P(T3); (8)T1 = P(A1 + T2) = P(A) + P(T2) - P(A) * P(T2) = P(A) + (1 - P(A)) * P(T2) = P(A) + P(A’)*P(T2); (9)T0 = P(A0 + T1) = P(A) + P(T1) - P(A) * P(T1) = P(A) + (1 - P(A)) * P(T1) = P(A) + P(A’)*P(T1); P(A) = 1 – 89 / 1024; P(A’)= 89 / 1024 则有: 将P(A)、P(A"""")代入(1) 有:T8 = 0.99244594573974609375 将P(A)、P(A"""")及P(T8)代入(2)有:T7 = 0.999343446455895900726318359375 将P(A)、P(A"""")及P(T7)代入(3)有:T6 = 0.99994293626423313980922102928162 将P(A)、P(A"""")及P(T6)代入(4)有:T5 = 0.99999144056433252438864656141959 将P(A)、P(A"""")及P(T5)代入(5)有:T4 = 0.99999925606467343229549760152958 将P(A)、P(A"""")及P(T4)代入(6)有:T3 = 0.99999993534155853073662039700794 将P(A)、P(A"""")及P(T3)代入(7)有:T2 = 0.99999999438027217698785079622432 将P(A)、P(A"""")及P(T2)代入(8)有:T1 = 0.99999999951156662475773312584372 将P(A)、P(A"""")及P(T1)代入(9)有:T0 = 0.9999999999575482710971076642579 由于: T0 = P(A0 + A1 + ... + A9); 所以: P = 0.9999999999575482710971076642579 答:因设赌者赢的概率为 P , 选择不赌 。 以上结果为什么 P 不等于 1 呢? 因此 , 可以猜想题所隐含的是一个“完备事件组” , 之所以 P ≠ 1 可能是纯数值计算误差所引起 。 本帖探讨 P = P(A0 + A1 + ... + A9) = 1 , 即 A0、A1 ... A9 为完备事件组 。


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