The science of comparative judgement began with Louis Leon Thurstone of the University of
Chicago. A pioneer of psychophysics, he proposed several ways to construct scales for
measuring sensation and other psychological properties. One of these was the Law of
comparative judgment (Thurstone, 1927a, 1927b), which defined a mathematical way of
modeling the chance that one object will ‘beat’ another in a comparison, given values for the
‘quality’ of each. This is all that is needed to construct a complete measurement system.
For more about this history of the use of this Law of Comparative Judgement in education,
please read more here.