在一定条件下,根据某事件发生与否可将所有事件分为必然事件、不可能事件和随机事件．一个随机事件发生既有随机性(对单次试验来说),又存在着统计规律性(对大量重复试验来说),这就是偶然性和必然性的对立统一．在大量n次重复试验中,事件A发生的次数为m次,它的频率f(A)=m/n．当n很大时,f(A)总是有规律地在某个常数值附近摆 Under certain conditions, all events can be classified into inevitable events, impossible events, and random events according to the occurrence of an event. The occurrence of a random event is both random (for a single experiment) and statistical regularity (for a large number of repeated tests), which is the opposite unity of chance and necessity. In a large number of n repeated trials, the number of occurrences of event A is m times, and its frequency f(A) = m/n. When n is large, f(A) always swings around a certain constant value regularly