Dispersion (variance)
$$DX = (x_1^{2}\cdot p_1+x_2^{2}\cdot p_2+x3^{2}\cdot p3)-(EX)^{2}$$
DX - dispersion
EX - mathematical expectation
x1, x2, x3 ... - posible values of event
p1, p2, p3 ... - probabilities of event
EX - mathematical expectation
x1, x2, x3 ... - posible values of event
p1, p2, p3 ... - probabilities of event
Find
It is known that:
= 