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对于随机变量X,原则上只要求出其分布列,就可以求出均值和方差,这一思想适用于所有的分布。而对于一些特殊的分布,在求均值与方差时,则可以直接用公式来求解。对于均值与方差有关的问题,其求解策略大致有三种方法:定义法、公式法、分解法。下面分类进行分析。一、基本策略——定义法一般分布有多种类型,有互斥事件的概率分布,也有相互独立事件的概率分布。服从一般分布的随机变量的均值与方差,可利用其定义式求解。而利用定义法求离散型随机变量的均值与方差的关键是正确列出
For the random variable X, in principle, as long as the distribution of its distribution, you can find the mean and variance, this idea applies to all distributions. For some special distributions, when calculating the mean and variance, you can directly use the formula to solve. There are roughly three methods for solving the problems related to the mean and variance: the definition method, the formula method, and the decomposition method. The following classification analysis. First, the basic strategy - the definition of a general distribution of a variety of types, there is a probability distribution of mutually exclusive events, but also the probability distribution of mutually independent events. The mean and variance of random variables subject to general distribution can be solved by using their definition formulas. The key to using the definition method to find the mean and variance of discrete random variables is to correctly list