What will be the variance of the following series ? X : -3 -2 3 8 9f : 5 4 22 4 5

14
15
18
20

The correct answer is (c) 18.

The variance of a set of numbers is a measure of how spread out the numbers are. It is calculated by taking the square of the difference between each number and the mean, and then averaging those squares.

In this case, the mean is $\frac{(-3) + (-2) + 3 + 8 + 9 + 5 + 4 + 22 + 4 + 5}{10} = \frac{43}{10}$.

The squared deviations from the mean are:

$(-3 – \frac{43}{10})^2 = \frac{9}{100}$
$(-2 – \frac{43}{10})^2 = \frac{49}{100}$
$(3 – \frac{43}{10})^2 = \frac{9}{100}$
$(8 – \frac{43}{10})^2 = \frac{169}{100}$
$(9 – \frac{43}{10})^2 = \frac{144}{100}$
$(5 – \frac{43}{10})^2 = \frac{49}{100}$
$(4 – \frac{43}{10})^2 = \frac{9}{100}$
$(22 – \frac{43}{10})^2 = \frac{329}{100}$
$(4 – \frac{43}{10})^2 = \frac{9}{100}$
$(5 – \frac{43}{10})^2 = \frac{49}{100}$

The variance is then $\frac{9}{100} + \frac{49}{100} + \frac{9}{100} + \frac{169}{100} + \frac{144}{100} + \frac{49}{100} + \frac{9}{100} + \frac{329}{100} + \frac{9}{100} + \frac{49}{100} = \frac{18}{5}$.

Multiplying by 5 to get the variance in the original units, we get 18.

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