Standard Deviation

Standard deviation is the square root of the variance, i.e. the square root of the mean of the squares of the deviations from the mean value of a vibrating quantity. The square of the standard deviation is the variance. An expression of the so-called "second moment," which describes the "dispersion" or variability around the mean.

In noise data, the standard deviation should be approximately the same as the rms.

for the data series: x₁, x₂, x₃,....,x_n the standard deviation of a sample, σ is:

The standard deviation of the entire population, σ_p

See also: Average Deviation, Mean, Standard Error, Statistic, Variance.