Sample variance (dispersion)

$s^{2} = x_1^{2}\cdot p_1+x_2^{2}\cdot p_2+x3^{2}\cdot p3-x_{v}^{2}$

s^2 - sample variance (dispersion)
x1, x2, x3 ... - sample values
p1, p2, p3 ... - relative frequencies of sample elements
x_v - sample mean (average)

Find It is known that:

Calculate 's'