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Inference under Covariate-Adaptive Randomization with Imperfect Compliance

Federico A. Bugni, Mengsi Gao

arXiv 7 Feb 2021 · Econometrics · publishedJournal of Econometrics (2023) · 2 citations (OpenAlex)

arXiv:2102.03937 · PDF · DOI · OpenAlex · Extracted main text

Abstract

This paper studies inference in a randomized controlled trial (RCT) with covariate-adaptive randomization (CAR) and imperfect compliance of a binary treatment. In this context, we study inference on the LATE. As in Bugni et al. (2018,2019), CAR refers to randomization schemes that first stratify according to baseline covariates and then assign treatment status so as to achieve "balance" within each stratum. In contrast to these papers, however, we allow participants of the RCT to endogenously decide to comply or not with the assigned treatment status. We study the properties of an estimator of the LATE derived from a "fully saturated" IV linear regression, i.e., a linear regression of the outcome on all indicators for all strata and their interaction with the treatment decision, with the latter instrumented with the treatment assignment. We show that the proposed LATE estimator is asymptotically normal, and we characterize its asymptotic variance in terms of primitives of the problem. We provide consistent estimators of the standard errors and asymptotically exact hypothesis tests. In the special case when the target proportion of units assigned to each treatment does not vary across strata, we can also consider two other estimators of the LATE, including the one based on the "strata fixed effects" IV linear regression, i.e., a linear regression of the outcome on indicators for all strata and the treatment decision, with the latter instrumented with the treatment assignment. Our characterization of the asymptotic variance of the LATE estimators allows us to understand the influence of the parameters of the RCT. We use this to propose strategies to minimize their asymptotic variance in a hypothetical RCT based on data from a pilot study. We illustrate the practical relevance of these results using a simulation study and an empirical application based on Dupas et al. (2018).

Citation extraction

17
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Most heavily cited references

The works this paper leans on most, across its whole bibliography — not restricted to papers in our corpus. Ranked by composite intensity, which combines how often a work is mentioned, how many sections mention it, and how much of that falls in the main text rather than the appendix.

ReferenceIntensityMentionsSectionsMain text
1Bugni, F. A., I. A. Canay, and A. M. Shaikh (2019) Inference under Covariate-Adaptive Randomization with Multiple Treatments self1.000215100%
2Dupas, P., D. Karlan, J. Robinson, and D. Ubfal (2018) Banking the Unbanked? Evidence from Three Countries1.000144100%
3Ansel, J., H. Hong, and J. Li (2018) OLS and 2SLS in Randomized and Conditionally Randomized Experiments1.00054100%
4Bugni, F. A., I. A. Canay, and A. M. Shaikh (2018) Inference under Covariate Adaptive Randomization self0.96721690%
5Hu, Y. and F. Hu (2012) Asymptotic properties of covariate-adaptive randomization0.87482100%
6Angrist, J. D. and G. Imbens (1994) Identification and Estimation of Local Average Treatment Effects0.81142100%
7Bai, Y (2022) Optimality of Matched-Pair Designs in Randomized Controlled Trials, Forthcoming in American Economic Review0.81142100%
8Pocock, S. J. and R. Simon (1975) Sequential treatment assignment with balancing for prognostic factors in the controlled clinical trial0.73732100%
9Tabord-Meehan, M (2020) Stratification Trees for Adaptive Randomization in Randomized Controlled Trials, Mimeo: University of Chicago0.69351100%
10Lin, W (2013) Agnostic notes on regression adjustments to experimental data: Reexamining Freedman’s critique0.64422100%

Showing the top 10 of 17 scored citations.

Cited by, within the corpus

arXiv econ.EM papers that cite this one, ranked by how heavily they lean on it.

Citing paperIntensityMentionsSections
1Improving Estimation Efficiency via Regression-Adjustment in Covariate-Adaptive Randomizations with Imperfect Compliance1.000114
2Identification and Inference on Treatment Effects under Covariate-Adaptive Randomization and Imperfect Compliance1.00083
3Stratification Trees for Adaptive Randomization in Randomized Controlled Trials0.84333
4Regression-Adjusted Estimation of Quantile Treatment Effects under Covariate-Adaptive Randomizations0.40511
5Inference in Experiments with Matched Pairs and Imperfect Compliance0.40511
6A Primer on the Analysis of Randomized Experiments and a Survey of some Recent Advances0.40511
7Misspecified regressions with mixed regressors: robust inference and causal interpretation0.00011