概率统计重概念 ,思想方法要熟练 .“随机”、“必然”、“不可能” ,三种事件要分辨 .“等可能性”求概率 ,排列组合能实现 .“互斥”、“对立”、“互独立” ,异同关系紧相连 .随机变量分布列 ,期望、方差是重点 .统计抽样有三法 ,“随机”、“系统”与“分层” .正态分布重 The concept of probabilistic statistics is heavy and the methods of thinking must be proficient. “Random,” “inevitable,” and “impossible,” three types of events must be distinguished. “Equal possibilities” require probability, and permutations and combinations can achieve “mutual exclusion” and “opposition”. “Interdependence” is closely related to similarities and differences. Random variable distribution, expectation and variance are the key points. Statistical sampling has three methods, “random”, “system” and “stratification”. Normal distribution weight