When to use an uncertainty estimate in a measurement?
1 Every measured result reported by a laboratory should be accompanied by an explicit uncertainty estimate. One purpose of this chapter is to give users of radioanalytical data an understanding of the causes of measurement uncertainty and of the meaning of uncertainty statements in laboratory reports.
How to find the relative uncertainty of a value?
The relative uncertainty gives the uncertainty as a percentage of the original value. Work this out with: Relative uncertainty = (absolute uncertainty ÷ best estimate) × 100% So in the example above: Relative uncertainty = (0.2 cm ÷ 3.4 cm) × 100% = 5.9% The value can therefore be quoted as 3.4 cm ± 5.9%.
What should be included in an uncertainty assessment?
The uncertainty assessment should include every conceivable or likely source of inaccuracy in the result. More recently ANSI N42.23, American National Standard Measurement and Associated Instru – ment Quality Assurance for Radioassay Laboratories
When to report counting uncertainty and total propagated uncertainty?
More recently ANSI N42.23, American National Standard Measurement and Associated Instru – ment Quality Assurance for Radioassay Laboratories , recommended that service laboratories report both the counting uncertainty and the total propagated uncertainty. ISO/IEC 17025,
How do you calculate percentage uncertainty in volume?
percentage uncertainty in volume = 3 * (percentage uncertainty in L) = 3 * 3.1% = 9.3%. When the power is not an integer, you must use this technique of multiplying the percentage uncertainty in a quantity by the power to which it is raised. If the power is negative, discard the negative sign for uncertainty calculations only.
How is trace ability defined in terms of uncertainty?
(see Chapter 18) is defined in terms of uncertainty. Trace ability is defined as the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties (ISO, 1993a). Thus, a labora
What does Nelac stand for in measurement uncertainty?
The National Environ- mental Laboratory Accreditation Conference (NELAC) has also published a standard on labora- tory quality systems, which requires a radiochemical testing laboratory to report with each result its associated measurement uncertainty (NELAC, 2002, ch. 5). Note that the concept of traceability