Question
Compute variance and standard deviation for the following data:

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Answer


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$\begin{aligned} & \bar{x}=\frac{\sum f _{ i } x_i}{ N }=\frac{542}{60}=9.03 \\ & \operatorname{Var}( X )=\sigma_x{ }^2=\frac{\sum f _{ i } x_i{ }^2}{ N }-(\bar{x})^2\end{aligned}$

$=\frac{6836}{60 \text {}}-(9.03)^2$

$\begin{aligned} & =113.93-81.54 \\ & =32.39\end{aligned}$

S.D. $=\sigma_x=\sqrt{\operatorname{Var}(X)}=\sqrt{32.39}=5.69$

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