A Weighting Method for Assessing Between-Site Heterogeneity in Causal Mediation Mechanism

Xu Qin and Guanglei Hong

Journal of Educational and Behavioral Statistics, 2017, vol. 42, issue 3, 308-340

Abstract: When a multisite randomized trial reveals between-site variation in program impact, methods are needed for further investigating heterogeneous mediation mechanisms across the sites. We conceptualize and identify a joint distribution of site-specific direct and indirect effects under the potential outcomes framework. A method-of-moments procedure incorporating ratio-of-mediator-probability weighting (RMPW) consistently estimates the causal parameters. This strategy conveniently relaxes the assumption of no Treatment × Mediator interaction while greatly simplifying the outcome model specification without invoking strong distributional assumptions. We derive asymptotic standard errors that reflect the sampling variability of the estimated weight. We also offer an easy-to-use R package, MultisiteMediation , that implements the proposed method. It is freely available at the Comprehensive R Archive Network ( http://cran.r-project.org/web/packages/MultisiteMediation ).

Keywords: asymptotic variance; direct effect; indirect effect; multilevel modeling; multisite randomized trials; method of moments; RMPW (search for similar items in EconPapers)
Date: 2017
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Persistent link: https://EconPapers.repec.org/RePEc:sae:jedbes:v:42:y:2017:i:3:p:308-340

DOI: 10.3102/1076998617694879

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