题目
设 X 是一个随机变量，EX = mu，DX = sigma^2 (mu, sigma > 0 为常数)，则对任意常数 c，必有A. E(X - c)^2 = EX^2 - c^2B. E(X - c)^2 = E(X - mu)^2C. E(X - c)^2 D. E(X - c)^2 geq E(X - mu)^2
设 $X$ 是一个随机变量，$EX = \mu$，$DX = \sigma^2$ ($\mu, \sigma > 0$ 为常数)，则对任意常数 $c$，必有
A. $E(X - c)^2 = EX^2 - c^2$
B. $E(X - c)^2 = E(X - \mu)^2$
C. $E(X - c)^2 < E(X - \mu)^2$
D. $E(X - c)^2 \geq E(X - \mu)^2$
题目解答
答案
D. $E(X - c)^2 \geq E(X - \mu)^2$