大家熟知:当已知随机变量ξ的分布列为P(ξ=x_k)=p_k(k=1,2,…)时,则有:Dξ=Eξ~2-(-Eξ)~2=(x_1-Eξ)~2 p_1+(x_2-Eξ)~2 p_2+…+(x_n-Eξ)~2 p_n+…≥0,可得知(Eξ)~2≤Eξ~2,当且仅当x_1=x_2=x_3=…=x_n=…=Eξ时,取等号.下面举例说明,利用构造随机变量ξ的分布列的方法,来解一些非常规随机变量ξ的分布列的最值问题,供读者们赏析参考. It is well known that when the distribution of random variables ξ is listed as P (ξ = x_k) = p_k (k = 1,2, ...), then Dξ = Eξ ~ 2 - (- Eξ) (Eξ) ~ 2≤Eξ ~ 2 can be obtained if and only if x_1 = x_2 = x_3 (x_2-Eξ) ~2 p_2 + ... + (x_n-Eξ) ~2 p_n + = ... = x_n = ... = Eξ, take the equal sign. The following example illustrates the use of the construction of a random variable ξ distribution of columns, to solve some of the unconventional random variable ξ distribution of the most value problems for readers to appreciate the reference .