Estimation of measurement uncertainty in chemical analysis
9. The ISO GUM Modeling approach
This section presents step by step the modeling approach to measurement uncertainty estimation. This approach is described in detail in the ISO GUM(2) and has been interpreted for chemistry in the Eurachem measurement uncertainty guide(3). It is often called also the “bottom-up” approach. This means that the uncertainties of the input quantities are found and thereafter combined into the combined standard uncertainty. The uncertainty estimation carried out in section 4 in principle also used this approach. The presentation in this section is based on a practical example – determination of ammonium nitrogen in water.
- 9.1. Step 1– Measurand definition
- 9.2. Step 2 – Model equation
- 9.3. Step 3 – Uncertainty sources
- 9.4. Step 4 – Values of the input quantities
- 9.5. Step 5 – Standard uncertainties of the input quantities
- 9.6. Step 6 – Value of the output quantity
- 9.7. Step 7 – Combined standard uncertainty
- 9.8. Step 8 – Expanded uncertainty
- 9.9. Step 9 – Looking at the obtained uncertainty
The slides used in this section can be downloaded from here:
