Propagation of variance uncertainty calculation for an autopsy tissue analysis
- Los Alamos National Lab., NM (United States)
When a radiochemical analysis is reported, it is often accompanied by an uncertainty value that simply reflects the natural variation in the observed counts due to radioactive decay, the so-called counting statistics. However, when the assay procedure is complex or when the number of counts is large, there are usually other important contributors to the total measurement uncertainty that need to be considered. An assay value is almost useless unless it is accompanied by a measure of the uncertainty associated with that value. The uncertainty value should reflect all the major sources of variation and bias affecting the assay and should provide a specified level of confidence. An approach to uncertainty calculation that includes the uncertainty due to instrument calibration, values of the standards, and intermediate measurements as well as counting statistics is presented and applied to the analysis of an autopsy tissue. This approach, usually called propagation of variance, attempts to clearly distinguish between errors that have systematic (bias) effects and those that have random effects on the assays. The effects of these different types of errors are then propagated to the assay using formal statistical techniques. The result is an uncertainty on the assay that has a defensible level of confidence and which can be traced to individual major contributors. However, since only measurement steps are readly quantified and since all models are approximations, it is emphasized that without empirical verification, a propagation of uncertainty model may be just a fancy model with no connection to reality. 5 refs., 1 fig., 2 tab.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 54540
- Journal Information:
- Health Physics, Journal Name: Health Physics Journal Issue: 1 Vol. 67; ISSN HLTPAO; ISSN 0017-9078
- Country of Publication:
- United States
- Language:
- English
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