Lab Samples: Traceable and Non-Traceable Measured Values¶
ConCertainty distinguishes between two types of lab samples – depending on whether the measured values obtained with them are traceable or not. This distinction determines which statements you can make about your measurements and which calculation steps are possible when determining measurement uncertainty.
Non-Traceable Measurements¶
By repeatedly measuring the same sample over time, you can determine whether the results are consistent: if the values show little scatter, the measurement is precise. Whether the measured value is correct – i.e., whether it accurately reflects the actual composition – cannot be derived from this.
This aspect feeds into the contribution to reproducibility of measurement uncertainty.
In ConCertainty, you create such samples as lab samples without certificate data.
Traceable Measurements¶
If a certificate with documented reference values is available for a sample – e.g., for a certified reference material (CRM) or a standard – your own measured values are traceable to these values. This allows you to check whether your own measured values agree with the certified values: a systematic deviation indicates a bias.
This aspect can feed into the determination of measurement uncertainty via the contribution to comparability (trueness).
In ConCertainty, you create such samples as lab samples with certificate data. The certificate contains, for each parameter:
- the certified value with unit
- the associated uncertainty
- the coverage factor k, if it deviates from the certificate-wide value for a specific parameter
Info
Lab samples with stored certificate data are marked in the overview list with a quality mark symbol.
Impact on Measurement Uncertainty Determination¶
The type of lab sample determines which calculation steps its measured values can feed into:
| Without Certificate Data | With Certificate Data | |
|---|---|---|
| Contribution to reproducibility | ✓ | ✓ |
| Contribution to comparability | – | ✓ |
If no measurement data is available for a parameter on a sample with certificate data, the comparability component for this parameter cannot be calculated – in this case, the calculation is automatically omitted.
Info
Make sure that the parameters listed in the certificate match the parameters of the test profile used. Only then can it be ensured that the sample can be fully used as a comparability sample.