[教學] 二項分布標準差的教法請益
我直接證明,學生全倒......
想請教大家有沒有比較直觀的方法或簡易的證明,ORZ
我這樣證:
由 Var(X) = E(X^2) - E(X)^2
= E(X^2) - (np)^2
所以只要算出 E(X^2) 代入整理就好了
由期望值定義 =>
E(X^2) = sigma(k from 0 to n) (k^2)P(X=k)
下去展開、約分、提出np、變數變換等等算出再代回,
學生真的沒這麼厲害,QQ
想請教大家這邊是怎麼教的,謝謝
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