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- Title
Baseline, Placebo, and Treatment: Efficient Estimation for Three-Group Experiments.
- Authors
Gerber, Alan S.; Green, Donald P.; Kaplan, Edward H.; Kern, Holger L.
- Abstract
Randomized experiments commonly compare subjects receiving a treatment to subjects receiving a placebo. An alternative design, frequently used in field experimentation, compares subjects assigned to an untreated baseline group to subjects assigned to a treatment group, adjusting statistically for the fact that some members of the treatment group may fail to receive the treatment. This article shows the potential advantages of a three-group design (baseline, placebo, and treatment). We present a maximum likelihood estimator of the treatment effect for this three-group design and illustrate its use with a field experiment that gauges the effect of prerecorded phone calls on voter turnout. The three-group design offers efficiency advantages over two-group designs while at the same time guarding against unanticipated placebo effects (which would undermine the placebo-treatment comparison) and unexpectedly low rates of compliance with the treatment assignment (which would undermine the baseline-treatment comparison).
- Subjects
EXPERIMENTAL design; MAXIMUM likelihood statistics; RANDOMIZED controlled trials; PATIENT compliance; VOTER turnout; MASS mobilization; ESTIMATION theory
- Publication
Political Analysis, 2010, Vol 18, Issue 3, p297
- ISSN
1047-1987
- Publication type
Article
- DOI
10.1093/pan/mpq008