Measurements in the social sciences – with ‘instruments’ such as questionnaires, ability tests, – in education, healthcare and so on, need metrological quality assurance. A patient, for instance, expects the same quality of care wherever and whenever provided. This is a challenge since the usual tools of statistics do not always work on the categorical scales typical of such measurements. Modelling a measurement system where the instrument is a human being, and where the output is a performance metric, i.e., how well the set-up performs an assessment, appears to be a way forward. This BEMC Colloquium will present the necessary tools, such as psychometric Rasch measurement theory, and will be followed by a hands-on workshop where you yourselves can analyse cases such as (i) the Quality of the BEMC Colloquium Series and (ii) a Healthy Lifestyle.