TY  - JOUR
AU  - Chassang,Sylvain
AU  - Miquel,Gerard Padro i
AU  - Snowberg,Erik
TI  - Selective Trials: A Principal-Agent Approach to Randomized Controlled Experiments
JF  - National Bureau of Economic Research Working Paper Series
VL  - No. 16343
PY  - 2010
Y2  - September 2010
UR  - http://www.nber.org/papers/w16343
L1  - http://www.nber.org/papers/w16343.pdf
N1  - Author contact info:
Sylvain Chassang
Department of Economics
Bendheim Hall 316
Princeton University
Princeton, NJ 08544-1021
E-Mail: chassang@princeton.edu

Gerard Padro i Miquel
STICERD
London School of Economics
Houghton Street
London, WC2A 2AE
UNITED KINGDOM
Tel: (44) (0) 2078523554
E-Mail: g.padro@lse.ac.uk

Erik Snowberg
Division of Humanities and Social Sciences
MC 228-77
California Institute of Technology
Pasadena, CA 91125
Tel: 626/395-4094
E-Mail: snowberg@caltech.edu
AB  - We study the design of randomized controlled experiments in environments where outcomes are significantly affected by unobserved effort decisions taken by the subjects(agents). While standard randomized controlled trials (RCTs) are internally consistent, the unobservability of effort provision compromises external validity. We approach trial design as a principal-agent problem and show that natural extensions of RCTs -which we call selective trials- can help improve the external validity of experiments. In particular, selective trials can disentangle the effects of treatment, effort, and the interaction of treatment and effort. Moreover, they can help experimenters identify when measured treatment effects are affected by erroneous beliefs and inappropriate effort provision.
ER  -