783620H / 1013 6. ANALYSIS METHODS
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All the quantities have been defined earlier except
γ, which is related to the confidence interval and 1
!γ is the probability that the measured value is within the confidence limits calculated (the typical value of
γ is 0.05 for 95% confidence).
According to ISO NORM Eq. 30 or F.17, the upper limit of the peak area is:
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If the uncertainty is small compared to the net peak area (i.e., when Q is large), then
ω is very close to 1. Under those conditions, N is in the middle of the confidence limits. When Q is small,
k p
is less than k
q
, so N is closer to the lower limit than the upper limit.
If the peak area uncertainty is zero (typically this happens when the net peak area is zero), the lower and upper confidence limits are set to zero.
Conversion from peak area limits to the corresponding activity limits is done through Eqs. 156 and 157.
6.17.6. Nuclide Calculation Details
The nuclide activity and its associated uncertainty are the branching-ratio weighted average of all the “qualifying” peaks of the nuclide (i.e., those that meet the criteria in Section 6.7.1 for inclusion in the average activity calculation). For all ISO NORM quantities (CL, MDA, etc.), if those qualifying peaks are found, then the ISO NORM results are also weighted using the branching ratios. Otherwise, ISO NORM quantities are calculated from the “MDA” line, which is typically the line used by GammaVision to calculate the MDA in regular analysis reports.
6.17.6.1. Nuclide Activity
In GammaVision, the final activity of the nuclide is the average of the peak activity of the qualifying peaks (per Section 6.7.1) defined in the library. If there are m qualifying lines for a nuclide, then the nuclide activity A
A
is the branching-weighted average of all qualifying peaks, as follows in this restatement of Eq. 60:
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