Over the past decade randomized field experiments have gained prominence in the toolkit of empirical economics and policy making. In an article titled "Field Experiments in Economics: The Past, the Present, and the Future," Levitt and List (2009) make three main claims about the history, philosophy, and future of field experiments in economics. (1) They claim that field experiments in economics began in the 1920s and 1930s in agricultural work by Neyman and Fisher. (2) They claim that artificial randomization is essential for good experimental design because, they claim, randomization is the only valid justification for Student's test of significance. (3) They claim that decision-making in private sector firms will be advanced by partnering with economists doing randomized experiments. Several areas of research have been influenced by the article despite the absence of historical and methodological review. This paper seeks to fill that gap in the literature. The power and efficiency of balanced over random designs — discovered by William S. Gosset aka Student, and confirmed by Pearson, Neyman, Jeffreys, and others adopting a balanced, decision-theoretic and/or Bayesian approach to experiments — is not mentioned in the Levitt and List article. Neglect of Student is regrettable. A body of evidence descending from Student (1911) and extending to Heckman and Vytlacil (2007) suggests that artificial randomization is neither necessary nor sufficient for improving efficiency, identifying causal relationships, and discovering economically significant differences. Three easy ways to improve field experiments are proposed and briefly illustrated.
Katika muongo uliopita randomized majaribio ya shamba wamepata umaarufu katika toolkit ya uchumi empirical na sera ya kutengeneza. Katika makala iliyoitwa Majaribio ya Shamba katika Uchumi: Nyakati za Kale, za Sasa na za Baadaye, Levitt na List (2009) hufanya madai matatu kuu kuhusu historia, falsafa, na siku zijazo za majaribio ya shamba katika uchumi. Majaribio ya shamba katika uchumi yalianza katika miaka ya 1920 na 1930 katika kazi ya kilimo na Neyman na Fisher. Kwa sababu randomization ni muhimu kwa ajili ya kubuni nzuri ya majaribio, randomization ni haki pekee halali kwa ajili ya mtihani wa umuhimu wa mwanafunzi. Wanasema kwamba maamuzi katika makampuni ya sekta binafsi yataendelezwa kwa kushirikiana na wachumi kufanya majaribio randomized. Maeneo kadhaa ya utafiti yameathiriwa na makala hiyo licha ya kukosekana kwa ukaguzi wa kihistoria na mbinu. Karatasi hii inatafuta kujaza pengo hilo katika fasihi. Nguvu na ufanisi wa usawa juu ya miundo ya nasibu - iligunduliwa na William S. Gosset aka Mwanafunzi, na kuthibitishwa na Pearson, Neyman, Jeffreys, na wengine kuchukua usawa, uamuzi-theoretic na / au Bayesian mbinu ya majaribio - haitajwi katika makala ya Levitt na Orodha. Kupuuzwa kwa Mwanafunzi ni jambo la kusikitisha. "Uchunguzi wa utafiti uliofanywa na Heckman na Vitalik, unaonyesha kwamba ""randomization bandia"" haipaswi kuwa na ufanisi, kutambua uhusiano wa sababu, na kugundua tofauti muhimu za kiuchumi." Njia tatu rahisi za kuboresha majaribio ya shamba zinapendekezwa na kuonyeshwa kwa ufupi.