Here we just have a quick post to highlight what are commonly the 10 most commonly used sources of uncertainty that we can use in our modelling and budgeting process. Obviously this is not an exhaustive list – just the most common. Once we know these are the most often used it is useful to look at them as a starting point when beginning to model our assays so that we can assess how much of our uncertainty is modelled by these factors.

In some cases we may think that one or two of these contributors are sufficient to define our MU. However, in some cases we will need more. Based on this assessment we all then be led to what is the most appropriate method to calculate our uncertainty in the following stages. So without any further ado, we count down what the sources we most often see are……….

10. Resolution – Significant Figures

9. Traceability

8. Inter Rater Agreement

7. Uncertainty Propagation – Calculated results

6. Calibration Uncertainty

5. External Quality Assurance

4. Reproducibility – Changes in reagents

3. Reproducibility – Difference between Analysers

2. Repeatability – Internal Quality Control


and the “winner” is………………




1. Definition of the Measurand

An absolute must. We cannot define our uncertainty without first defining what we are measuring. This should be included in every uncertainty budget, and as such is well placed here at number one in our most commonly used source of uncertainty for any uncertainty budget.