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Mathematics · 术语表

什么是 Expectation, variance, standard deviation？

又称： expectation · variance

Definition 33.2 High School Mathematics · 第 33 章 — Random Variables and the Binomial Distribution

The expectation of $X$ is

$$\E(X) = \sum_{i=1}^{k} p_i\, x_i ,$$

its variance and standard deviation are

$$\V(X) = \E\bigl((X - \E(X))^2\bigr) = \sum_{i=1}^k p_i\bigl(x_i - \E(X)\bigr)^2, \qquad \sigma(X) = \sqrt{\V(X)} .$$

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相关术语

• Variance, standard deviation