Founded in 1958, the International Measurement Confederation (IMEKO) is a voluntary, non-governmental federation of 42 metrological organizations from all over the world.  Its mission is to enhance international co-operation among scientists and engineers from research and industry. This month saw the XXII World Congress of IMEKO, held in the Belfast, UK and hosted by the Institute of Measurement and Control with support from the National Physical Laboratory. Its theme was ‘Knowledge Through Measurement’, leading on from the work of the Belfast-born scientist William Thompson (Lord Kelvin), who famously wrote:
“I often say that when you can measure what you are speaking about and express it in numbers you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.” 
Excitingly for the first time, social scientists were invited to take part in special dedicated session . Chaired by Professor Mark Wilson and Dr William Fisher, the session included six talks from speakers from academia and industry, including Modus Outcomes’ Stefan Cano and Thomas Salzberger (Table 1).
Did you know…
Measurement can be defined as a quantitative comparison, made using one of more instruments, in a unit with expressed measurement uncertainty . Metrology, then, can be defined as “the science of measurement, embracing both experimental and theoretical determinations at any level of uncertainty in any field of science and technology” . Modern metrology dates back to the late eighteenth century through the efforts to harmonize units throughout France . The meter and subsequently the metric system were born, eventually leading to the International System of Units (SI) in 1960 . Today, most countries have national metrology institutes (NMI) and national measurement systems (NMS), which take the form of a network of laboratories, calibration facilities and accreditation bodies that implement and maintain its metrology infrastructure.
Metrology is important because standardization of units is critical for measurements to be meaningful in linking human endeavors, including: economics, energy, environment, health, manufacturing, industry and consumer confidence . There are three broad types of metrology (Table 2), which all involve three cornerstone activities: the definition of internationally accepted units of measurement; the realization of these units of measurement in practice; and the application of chains of traceability (i.e., linking measurements to reference standards) .
Metrology provides a framework for a common language of reference measurement systems, which in turn have the potential to improve the accuracy and comparability of data from different sources. However, we have yet to realize reconciliation between metrology in the physical sciences and measurement practices in the social sciences , despite the extensive and long running history of social measurement . However, in recent years this situation is beginning to change. This is exemplified by the commercially successful  scientific reading ability measurement framework , collaborations between metrology engineers and psychometricians , and new research being produced within national metrology institutes [22-25].
In a recent blog, William Fisher (a member of Modus Outcomes Scientific Advisory Group), offers a measurement quality checklist , which helps move us away from the ambiguity of psychometric statistics  and towards a fuller understanding of scales and tests social scientists like to call ‘instruments’ (Box 1).
There are lots of possible reasons for the lack of recourse to formal metrological frameworks in the social sciences . But, at a time when Patient Centered Outcome Measures are being used in high stakes decision making across clinical research, trials and practice, we believe it essential that our instruments reach the highest possible scientific bar . As we have seen, the potential damage caused by not-fit-for-purpose scales can be profound  .
Measurement in the social sciences currently resembles the problem that was measurement of temperature in the 17th Century . Reconciliation between metrology in the physical sciences and measurement in the social sciences can help to provide a resolution. We at Modus Outcomes will continue to pursue our collaborations with metrological researchers, societies, and national institutes to further support the case to move towards higher standards for measurement to ensure that potential benefit of new therapies is evaluated accurately and fairly.
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