引用第0樓vincent於2011-09-22 22:49發表的“Statistics Questions (each 250好友元)”:
Assume that every time you buy an item of the HK Disney series, you receive one of the four types of cards, each with a cartoon character Mickey, Minnie, Donald and Daisy with an equal probability. Over a period of time, you buy 6 items of the series. What is the probability that you will get all four cards?
If n persons, including A and B, are randomly arranged in a straight line, what is the probability that there are exactly r persons in the line between A and B?
1.) (4P4 x 6P2) / (4C1)^6 = 0.176