概率计算中应区分的三类概念

Distinguish Three Kinds of Conceptions in the Calculation of Probability

通过对“有放回”与“无放回”、“排列”与“组合”、“相同”与“不同”三类概念区别的分析。

This article clarifies the differences among 3 pairs of conceptions：“replacement”and“nom- replacement”,“arrange”and“constitute”,“identical”and“different”for avoiding confusing them.