A duplicate error ratio, or DER, is used to represent the precision of a measurement. It is used most often when measuring radionuclide activity and water quality parameters. The goal of the DER is to show how often a measurement would be duplicated if it was taken under the exact conditions. Therefore, it is a quantitative measure of the accuracy of the data point. Additional values, such as the total propagated uncertainty of the data, is needed for the calculation.
Instructions
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1
Square the sample's total unpropagated uncertainty. This value is usually denoted by TPUs.
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2
Square the duplicate's total unpropagated uncertainty. This value is usually denoted by TPUd.
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3
Sum the results from Step 1 and Step 2 and take the square root of the resulting value.
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4
Subtract the duplicate result, D, from the sample result, S.
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5
Divide the value from Step 4 by the value from Step 3 to yield the DER. The final equation should read DER = (S - D) / sqrt(TPUs^2 + TPUd^2).