% Diff and Variation (%RSD) calculations

ramorri

Hi,

I was just curious how %Diff and Variation (%RSD) is calculated in the QAQC secondary check?

I was assuming % Diff is: [known - measured]/[(known + measured)/2]*100, but I am getting very slightly different results, so maybe the iolite calculation considers uncertainty on known values? Or perhaps the difference is just from rounding?

And for %RSD I assume it's calculated: (stdev/mean)*100

Thanks for any clarification! I will poke around in the paper references & webinars in the meantime to see if I can find anything...
Rebecca

Bence

Hi Rebecca,

The percentage diff is calculated as (group_mean - accepted) / accepted x 100 as it is the difference from the accepted value expressed as a percentage.

Your formula for the %RSD is correct, but just note that it is the group st dev and group mean.

Kind regards,
Bence

ramorri

Great, thanks Bence!

Rebecca