Uncertainty of measurement (UoM) is the doubt that exists about the result of any measurement.
For every measurement there is always a margin of doubt:
For example, the length of a certain stick measures 20 centimetres plus or minus 1 centimetre, at the 95 percent confidence level. This means we are 95 percent sure that the stick is between 19 centimetres and 21centimetres long.
UKAS (SMTL's accreditation body) requires laboratories to report the uncertainty of test results and test certificates under relevant circumstances. SMTL therefore report our UoM in an Annex to our test reports where this is relevant. This allows the client to assess the impact of the UoM against the specification.
If a client requires the UoM to be taken into account when we assess compliance with a limit, then the client must explicitly make this requirement known to SMTL when they sign the RFW (Request for Work contract). This can be done by amending the "ANY OTHER REQUIREMENTS" section of the RFW.
Therefore, unless otherwise required, SMTL will use the shared risk model using the binary simple acceptance rule (as per ILAC G8) for the decision rules.
In general, SMTL use the "Round to Nearest" rule for non-tied values (i.e. those values which do not end in a 5) and follows the IEEE "Round half to Even" rule for tied or mid-point values.
When results are calculated using a 3rd party validated software, manual calculations may differ slightly due to rounding, however, SMTL will accept figures provided by the software regardless of the method used.