Measurement Uncertainty for VGT Accredited Test Methods

When scientists make a measurement or calculate some quantity from their data, they generally assume that some exact or "true value" exists based on how they define what is being measured (or calculated).  Scientists reporting their results also calculate a range of values that they expect this "true value" to fall within, based on expected errors associated with that measurement.  This range is called the Measurement Uncertainty and is assessed at a particular result value. 

When assessing whether a result is within compliance or not, it may be necessary to take account of the measurement uncertainty range that the result reported may fall into.  As an example, if a Total Suspended Solids result is reported as 50 mg/L, the measurement uncertainty associated with that result has been calculated as ±2 mg/L, then it is possible that the “true value” is somewhere between 48 and 52 mg/L.

The measurement uncertainty for VGT’s accredited tests is given below.