“4个可分辨的球 ,随机地投入 3个盒中 ,试求3盒都不空的概率 .”这是一道很容易做错的概率题 .比较典型的有下面两个错解 :错解 1　设Ａ=“三盒都不空” ,基本事件总数为 3 4 .有利于Ａ的基本事件数可按下面两步来计算 :第一步 ,从 4球中任取 3球 ,将它们每盒一球地放入 3个盒 “4 resolvable balls, randomly put into 3 boxes, try the probability that 3 boxes are not empty.” This is a probability question that is easy to do wrong. There are two typical mistakes: misinterpretation 1 Let A=“three boxes are not empty” and the total number of basic events is 3 4. The number of basic events that favors A can be calculated in the following two steps: In the first step, take 3 balls from any of the 4 balls and put them each Box puts 3 boxes in a ball