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# The standard deviation of -1, -2, -3, -4, -5, -6, -7 is

$\begin {array} {1 1} (A)\;2 & \quad (B)\;4 \\ (C)\;-2 & \quad (D)\;-4 \end {array}$

Can you answer this question?

$AM = \large\frac{-(1+2+....+7)}{7}$
$= -\large\frac{28}{7}$ $= -4$
$\therefore \sigma^2 = \large\frac{\Sigma x_i^2}{n}$ $- ( \overline x)^2=4$
$\sigma = 2$
Ans : (A)
answered Jan 28, 2014