Statistics

Sample width
r = x_d - x_m

Sample center
c = (x_d + x_m) / 2

Relative frequency
p_k = m_k / n

Sample mean
x_v = (x1+ x2 + x3) / n

Sample mean
x_v = (x1*m1+ x2*m2 + x3*m3) / n

Sample variance (dispersion)
s^2 = ( (x1 - x_v)^2+ (x2 - x_v)^2 + (x3 - x_v)^2 ) / (n-1)

Sample variance (dispersion)
s^2 = ( (x1 - x_v)^2 * m1+ (x2 - x_v)^2 * m2 + (x3 - x_v)^2 *m3) / (n-1)

Sample variance (dispersion)
s^2 = x1^2 * p1 + x2^2 * p2 + x3^2 * p3 - x_v^2

Standard deviation
s = saknis(s^2)