standard deviation and rms values

from 20130510-WindTunnelMeas.ipynb


The formula used for calculating rms values was, $rms = \sqrt{ \frac{1}{n} \sum{x^{2}} }$

The standard deviations are of the quantity described and
were calculated using the population standard deviation calculation:
$std = \sqrt{ \frac{ \sum{ (x_{i} - \overline{x}) }^2}{n}} = \sqrt{variance}$.

It is clear that the standard deviation forms an rms like parameter, but using the
difference between each value and the mean, rather than the values themselves.  std should
therefore be compared to rms values, not amplitude values.