The Entry of Randomized Assignment into the Social Sciences

Although the concept of randomized assignment in order to control for extraneous confounding factors reaches back hundreds of years, the first empirical use appears to have been in an 1835 trial of homeopathic medicine. Throughout the 19th century there was a growing awareness of the need for comparison groups, albeit often without the realization that randomization could be a clean method to achieve that goal. In the second and more crucial phase of this history, four separate but related disciplines introduced randomized control trials within a few years of one another in the 1920s: agricultural science; clinical medicine; educational psychology; and social policy (specifically political science). This brought increasing rigor to fields that were focusing more on causal relationships. In a third phase, the 1950s through 1970s saw a surge of interest in more applied randomized experiments in economics and elsewhere – both in the lab and especially in the field.