Artel Blog Comment on Lab Report 4: Defining Accuracy, Precision and Trueness by Artel-usa

In reply to <a href="https://www.artel.co/learning_center/defining-accuracy-precision-and-trueness/#comment-31">Jacob Inglis</a>. Hi Jacob, According to a note in the VIM definition (clause 2.14) "Measurement trueness is not a quantity and thus cannot be expressed numerically..." So we are left with Trueness being a conceptual term meaning closeness of agreement between two things. The two things in this case are a reference value, and what the measured quantity would be if there were no random errors. The VIM points to other standards for defining "measures of closeness of agreement". The VIM specifically mentions that ISO 5725 contains measures (equations) for closeness of agreement. For liquid handling ISO 8655 and ISO IWA 15 give equations for calculating Systematic Error (SE). There are alternative forms of the equation, the units can be either liters (e.g., microliters) or dimensionless (%). So it's always good to include the units and reference what standard the equation came from. So maybe the way to answer a person who asks you to calculate Trueness would be to say "Trueness is a concept for closeness of agreement. Nobody can calculate a value for a concept, but what I can do is use the standard equations of Systematic Error which is the way that we measure closeness of agreement." You are correct about the backwards relationship between Trueness (which is good thing) and Error (being a bad thing). There is a second note in the VIM clause 2.14, which says "Measurement trueness is inversely related to systematic measurement error'. So large SE is "less Trueness", but we shouldn't try to write that in an equation. These are very specialized points, but I'm glad you are interested. Let's continue the discussion!