Numbers and measurement: a critique of evidence-based practice in psychology

Abstract Although psychology was established as a discipline more than one hundred years ago, it is far from homogeneous. On the contrary, it consists of several different schools. Evidence-based practice in psychology (EBPP) purports to be a neutral or pan-theoretic approach. The core of EBPP is randomized clinical trials (RCT). This paper traces the origins of RCT from the ideal of physics and shows how this ideal was exported to the social sciences and psychology. It particularly emphasizes the role of numbers and scales for quantitative measurements and shows that EBPP is built on these ideals. The paper concludes that psychology should be a pluralistic science, including different kinds of scientific knowledge.