Key Topics

Why is measurement uncertainty important?

Measurements are always made for a reason – to answer a particular question or to help solve a problem. The results from chemical analysis are used to answer a wide range of questions such as: ‘Does a pharmaceutical product contain the correct amount of active ingredient?’; ‘Is the level of alcohol in a blood sample in excess of the drink-drive limit?’; ‘Are the levels of pesticides in foodstuffs below the legal limits for pesticide residues?’.

Knowledge of the uncertainty associated with measurement results allows a judgement to be made as to whether the data are likely to be ‘fit for purpose’. In some cases a relatively large uncertainty might be acceptable, while in others this would make the results unusable.

If comparisons of results are being made, for example in determining whether a limit has been exceeded or whether the results produced by two laboratories are genuinely different, a meaningful interpretation of the results can only be achieved if the uncertainty is known.

Although uncertainty means ‘doubt’, having knowledge of the measurement uncertainty means that more is known about the result as the ‘doubt’ can be quantified.