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This report presents new statistical results for the sampling distribution of the D statistic. These results are of general application and are valid whatever the operator and inspector measurement methods. An expression for the sampling variance of the D statistic is derived without making any assumption about the cause (diversion, clerical error, measurement error) of the discrepancy. The sampling variance is the sum of two terms. The first represents the uncertainty due to the sampling of a finite population of discrepancies. The second term is the sampling average of the inspectors measurement uncertainty of the sample set of items. In a second result the paper shows how the sampling variance can be estimated using only the operators declared values, the inspectors measured values and the uncertainty of the inspectors measurements. This estimation theorem is valid for any inspector measurement method. In international safeguards the D statistic is used to estimate the total inventory discrepancy in a situation where nothing can be assumed about the cause of the discrepancy. The problem of assigning an uncertainty to the D statistic value without any diversion strategy assumptions has long been an unresolved problem. The results described in this paper provide the solution to this problem for any measurement system. The results of the paper are applied to derive the data evaluation algorithms for a photo neutron active interogation device (PHONID) for the assay of 235-U in bulk quantities. The paper also provides a general discussion of the distinction between planning a verification and performing the data analysis after the verification has been carried out.

Additional information

Bibliographic Reference: EUR 9230 EN (1984) MF, 65 P., BFR 120, BLOW-UP COPY BFR 325, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
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