Livermore Pu Measurements, Detection Limits and Uncertainty

["Erik C. Nielsen" <nielsenec@earthlink.net>]

Radiochemistry analytical results are composed of three numbers:  the
result, an analytical uncertainty and a Lower Limit of Detection (LLD) or
MDC (Minimum Detectable Concentration).

When interpeting analytical results, the first step is to compare the
result to the LLD/MDC.  This is usually calculated at the 95% confidence
level (4.66 constant) that a result greater than the LLD/MDC is real.  Once
this decision is made, the uncertainty is used to bracket the true value
within a certain degree of statistical confidence (1 sigma=65%, 1.96
sigma=95%).

This is supposed to be a two part process.  The fact that the uncertainty
subracted from the analytical result may be less than the LLD/MDC does not
mean that the activity is not present.

 
Erik C. Nielsen
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Opinions are my own.  Standard denials apply.
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