Arithmetic Standard Deviation - 2nd moment

Description

Shows how much variation or dispersion from the average exists, on the particles’ size distribution of a soil, in metric scale. Arithmetic mean size (1st moment) needs to be precalculated.

Related formulas

Variables

σaArithmetic Standard Deviation - 2nd moment (mm)
fiCumulative weight percent of the i particle size grade present (dimensionless)
mmmMid-point of the i particle size grade present (mm)
XaArithmetic mean size - 1st moment (mm)