By Levi Clancy for Student Reader on
This can either be presented by giving the minimum and maximum (ie, 100 to 150) or just the amount between (ie, 50).
σ2 = (Σ(x-µ)2)/N
Population Standard Deviation (σ)
σ = √σ2
Sample Standard Deviation
Mean absolute deviation
Mean absolute deviation from the mean measures dispersion but not often used. Mathematically better is the sample standard deviation, which is the square root of the sample variance. MAD = [ Σ | X - X | ] / n