A randomized experiment comparing random and cutoff-based assignment

William R. Shadish*, Rodolfo Galindo, Vivian C. Wong, Peter M. Steiner, Thomas D. Cook

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


In this article, we review past studies comparing randomized experiments to regression discontinuity designs, mostly finding similar results, but with significant exceptions. The latter might be due to potential confounds of study characteristics with assignment method or with failure to estimate the same parameter over methods. In this study, we correct the problems by randomly assigning 588 participants to be in a randomized experiment or a regression discontinuity design in which they are otherwise treated identically, comparing results estimating both the same and different parameters. Analysis includes parametric, semiparametric, and nonparametric methods of modeling nonlinearities. Results suggest that estimates from regression discontinuity designs approximate the results of randomized experiments reasonably well but also raise the issue of what constitutes agreement between the 2 estimates.

Original languageEnglish (US)
Pages (from-to)179-191
Number of pages13
JournalPsychological methods
Issue number2
StatePublished - Jun 2011


  • Cutoff-based assignment
  • Randomized experiment
  • Regression discontinuity design

ASJC Scopus subject areas

  • Psychology (miscellaneous)


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