Abstract
Abstract In the 1960s, Randomized Controlled Trial (RCT) was established as a ‘gold standard’ in clinical trial. Since the 1980s, RCT-method has gradually adopted in field experi-ments in economics and greatly influenced empirical economics. Based on the success of clinical trial, some empirical economists feel that RCT is also a ‘gold standard’ that provides objective evidence in policy-making procedures. This thesis, will consider (a) why the RCT-method becomes popular among empirical economists? (2) Can RCTs in economic research truly confirm causal hypotheses? Are there any theoretical limi-tations in the RCT methodology? (3) Does any real practice correspond to these limi-tations? Three brief conclusions are, first, RCT solves the problem of passive observation, which bothered traditional econometrics, and RCT as a policy tool is proved to be ‘objective’. Second, in the methodological figure we proposed, practicing economists and scientists may confront ‘idealization gaps’ and ‘generalization gaps’ that threaten the internal validity and external validity of field RCTs, respectively. Lastly, we take two class-size deduction cases: the Project STAR in Tennessee and the CSR Program in California as examples. The results indicate that the ‘generalization gaps’ are huge, and the ‘idealization gaps’ in these are still to be verified.