一类离散型随机变量的期望与方差的简单解法

A Simple Way of Computing the Mathematical Expectation and Variance of Discrete Random Variables

在计算离散型随机变量的期望与方差的过程中，使用定义计算往往比较困难，本文介绍了两种简单方法：将随机变量进行分解、利用离散型随机变量分布律的性质。这两种方法大大简化了计算，对随机变量的期望与方差的学习具有一定的启发和价值。

It's usually difficult to compute the mathematical expectation and variance of discrete random variables by defini-tion. This paper proposes two simple methods as resolving the random variable and using the probability distribution of discrete random variable. Results show that the two methods can simplify calculations, which have great enlightening significance and reference value to study of the mathematical expectation and variance of discrete random variables.