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Second moment from variance

EasyRandom VariablesStatistics~2m

A random variable XX has Var⁡(X)=25\operatorname{Var}(X) = 25 and E[X]=3\mathbb{E}[X] = 3. Find E[X2]\mathbb{E}[X^2].

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  1. Var⁡(X)=E[X2]−E[X]2\operatorname{Var}(X)=\mathbb{E}[X^2]-\mathbb{E}[X]^2.
  2. So E[X2]=25+32\mathbb{E}[X^2]=25+3^2.

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Asked at: IMC, Two Sigma

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