calculating first and second moments

[sepscientologist]

I'm trying to determine diffusion coefficient from the flow profile of an analyte injected into a stream of toluene by it's time vs UV
data. I have time (t) in seconds and UV absorbance (h) in mAU. I calculated M0 as the sum of the h values.

Is M1 just 1/M0 * sum of the h*t?
What is M2?

Thanks,
Marc

[tom jupille]

I've always worked with the definitions that:
M0 = area (so, h*t in your case; this is usually normalized to be unity).
M1 = mean
M2 = variance
M3 = skewness

If you can wade through the math (my eyes glaze over!), more detailed discussion is here:
http://en.wikipedia.org/wiki/Moment_%28 ... he_moments