The variance of the first n natural numbers i | vedclass

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Question

(A) The variance $\sigma^2$ is given by the formula $\sigma^2 = \frac{1}{n} \sum_{i=1}^{n} x_i^2 - \left( \frac{1}{n} \sum_{i=1}^{n} x_i \right)^2$. F

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$\frac{n^2 - 1}{12}$

Vedclass · Answer

(A) The variance $\sigma^2$ is given by the formula $\sigma^2 = \frac{1}{n} \sum_{i=1}^{n} x_i^2 - \left( \frac{1}{n} \sum_{i=1}^{n} x_i \right)^2$. For the first $n$ natural numbers,$\sum x_i = \frac{n(n+1)}{2}$ and $\sum x_i^2 = \frac{n(n+1)(2n+1)}{6}$. Substituting these values: $\sigma^2 = \frac{n(n+1)(2n+1)}{6n} - \left( \frac{n(n+1)}{2n} \right)^2$ $\sigma^2 = \frac{(n+1)(2n+1)}{6} - \frac{(n+1)^2}{4}$ $\sigma^2 = \frac{2(n+1)(2n+1) - 3(n+1)^2}{12}$ $\sigma^2 = \frac{(n+1) [2(2n+1) - 3(n+1)]}{12}$ $\sigma^2 = \frac{(n+1) [4n + 2 - 3n - 3]}{12}$ $\sigma^2 = \frac{(n+1)(n-1)}{12} = \frac{n^2 - 1}{12}$.

Class Interval	$0$-$5$	$5$-$10$	$10$-$15$	$15$-$20$	$20$-$25$
Frequency	$4$	$1$	$10$	$3$	$2$

The variance of the first $n$ natural numbers is

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