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Stratification Trees for Adaptive Randomization in Randomized Controlled Trials

Max Tabord-Meehan

arXiv 13 Jun 2018 · Econometrics · publishedThe Review of Economic Studies (2022) · 26 citations (OpenAlex)

arXiv:1806.05127 · PDF · DOI · OpenAlex · Extracted main text

Abstract

This paper proposes an adaptive randomization procedure for two-stage randomized controlled trials. The method uses data from a first-wave experiment in order to determine how to stratify in a second wave of the experiment, where the objective is to minimize the variance of an estimator for the average treatment effect (ATE). We consider selection from a class of stratified randomization procedures which we call stratification trees: these are procedures whose strata can be represented as decision trees, with differing treatment assignment probabilities across strata. By using the first wave to estimate a stratification tree, we simultaneously select which covariates to use for stratification, how to stratify over these covariates, as well as the assignment probabilities within these strata. Our main result shows that using this randomization procedure with an appropriate estimator results in an asymptotic variance which is minimal in the class of stratification trees. Moreover, the results we present are able to accommodate a large class of assignment mechanisms within strata, including stratified block randomization. In a simulation study, we find that our method, paired with an appropriate cross-validation procedure ,can improve on ad-hoc choices of stratification. We conclude by applying our method to the study in Karlan and Wood (2017), where we estimate stratification trees using the first wave of their experiment.

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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
1Karlan, Dean and Daniel H Wood (2017) The effect of effectiveness: Donor response to aid effectiveness in a direct mail fundraising experiment1.000144100%
2Bai, Yuehao (2019) Optimality of matched-pair designs in randomized controlled trials0.87462100%
3Bugni, Federico A and Mengsi Gao (2021) Inference under covariate-adaptive randomization with imperfect compliance0.84333100%
4Bugni, Federico A, Ivan A Canay, and Azeem M Shaikh (2018) Inference under covariate adaptive randomization with multiple treatments. bugni20170.81711455%
5Hahn, Jinyong, Keisuke Hirano, and Dean Karlan (2011) Adaptive experimental design using the propensity score0.8115280%
6Antognini, Alessandro Baldi and Alessandra Giovagnoli (2004) A new Ôbiased coin designÕfor the sequential allocation of two treatments0.64422100%
7Athey, Susan and Guido Imbens (2016) Recursive partitioning for heterogeneous causal effects0.64422100%
8Efron, Bradley (1971) Forcing a sequential experiment to be balanced0.64422100%
9Glennerster, Rachel and Kudzai Takavarasha (2013) Running randomized evaluations: A practical guide0.64422100%
10Hahn, Jinyong (1998) On the role of the propensity score in efficient semiparametric estimation of average treatment effects0.64422100%

Showing the top 10 of 66 scored citations.

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1Best Arm Identification with Contextual Information under a Small Gap0.73732
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4Regression-Adjusted Estimation of Quantile Treatment Effects under Covariate-Adaptive Randomizations0.51121
5The Role of Contextual Information in Best Arm Identification0.51121
6Improving Estimation Efficiency via Regression-Adjustment in Covariate-Adaptive Randomizations with Imperfect Compliance0.51121
7On the Performance of the Neyman Allocation with Small Pilots0.51121
8Inference under Covariate-Adaptive Randomization with Multiple Treatments0.40511
9Bootstrap Inference for Quantile Treatment Effects in Randomized Experiments with Matched Pairs0.40511
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