Measurement uncertainty guides

Short, practical explanations of the methods behind the calculator, each with a worked example you can open and change. Written by a metrologist, based on JCGM 100:2008 (GUM), EA-4/02 M:2022 and ILAC G8:09/2019.

• How to make a measurement uncertainty budget, step by step The seven steps from the measurement model to the reported U, with a complete worked example for a digital thermometer at 50 °C.
• Type A and Type B uncertainty: which divisor to use Turning readings, certificates and ± limits into standard uncertainties: s/√n, U/k, and the √3, √6 and √2 divisors.
• Coverage factor k and the Welch–Satterthwaite formula Why k = 2 can underestimate U with few readings, how to calculate νeff, and a table of k values for 95.45 %.
• Decision rules: simple acceptance, guard bands and ILAC G8 Simple acceptance vs guarded acceptance, the four ILAC G8 statements, false-accept risk, and what ISO/IEC 17025 asks for.
• Test uncertainty ratio (TUR): what 4:1 really means How to calculate TUR, TUR vs TAR, where 4:1 comes from, and why TUR alone does not protect results near the limit.