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Subject Rational Expectations Will Contaminate Randomized Controlled Medical Trials

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  • Chemla, Gilles
  • Hennessy, Christopher

Abstract

We develop a rational expectations model of placebo effects. If subjects in seemingly-ideal single-stage RCTs form rational beliefs about breakthroughs based upon personal physiological responses, mental effects differ across medications received, treatment versus control. Consequently, the average cross-arm health difference becomes a biased estimator of the mean non-placebo physiological effect. Constructively, we show: bias can be altered through choice of control; high-efficacy controls mitigate upward bias; and unbalanced panels may be preferred since bias approaches zero as treatment probability approaches zero. Consistent with experimental evidence, our theory implies outcomes within-arm and cross-arm differences can be non-monotone in treatment probability.

Suggested Citation

  • Chemla, Gilles & Hennessy, Christopher, 2016. "Subject Rational Expectations Will Contaminate Randomized Controlled Medical Trials," CEPR Discussion Papers 11360, Centre for Economic Policy Research.
    • Handle: RePEc:cpr:ceprdp:11360
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    File URL: https://cepr.org/publications/DP11360
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    References listed on IDEAS

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    1. Angus Deaton, 2010. "Instruments, Randomization, and Learning about Development," Journal of Economic Literature, American Economic Association, vol. 48(2), pages 424-455, June.
    2. Tat Y. Chan & Barton H. Hamilton, 2006. "Learning, Private Information, and the Economic Evaluation of Randomized Experiments," Journal of Political Economy, University of Chicago Press, vol. 114(6), pages 997-1040, December.
    3. Joshua D. Angrist & Jörn-Steffen Pischke, 2009. "Mostly Harmless Econometrics: An Empiricist's Companion," Economics Books, Princeton University Press, edition 1, number 8769, December.
    4. repec:pri:rpdevs:deaton_instruments_randomization_learning_all_04april_2010 is not listed on IDEAS
    5. Anup Malani, 2006. "Identifying Placebo Effects with Data from Clinical Trials," Journal of Political Economy, University of Chicago Press, vol. 114(2), pages 236-256, April.
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    JEL classification:

    • C10 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods and Methodology: General - - - General
    • C90 - Mathematical and Quantitative Methods - - Design of Experiments - - - General
    • D04 - Microeconomics - - General - - - Microeconomic Policy: Formulation; Implementation; Evaluation
    • I11 - Health, Education, and Welfare - - Health - - - Analysis of Health Care Markets
    • K32 - Law and Economics - - Other Substantive Areas of Law - - - Energy, Environmental, Health, and Safety Law
    • O3 - Economic Development, Innovation, Technological Change, and Growth - - Innovation; Research and Development; Technological Change; Intellectual Property Rights

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