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Bayesian Inference for Sequential Treatments under Latent Sequential Ignorability

Mattei, Federico; Ricciardi, Alessandra; Mealli, Fabrizia; (2020) Bayesian Inference for Sequential Treatments under Latent Sequential Ignorability. Journal of the American Statistical Association , 115 (531) pp. 1498-1517. 10.1080/01621459.2019.1623039. Green open access

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Abstract

We focus on causal inference for longitudinal treatments, where units are assigned to treatments at multiple time points, aiming to assess the effect of different treatment sequences on an outcome observed at a final point. A common assumption in similar studies is Sequential Ignorability (SI): treatment assignment at each time point is assumed independent of unobserved past and future potential outcomes given past observed outcomes and covariates. SI is questionable when treatment participation depends on individual choices, and treatment assignment may depend on unobservable quantities associated with future outcomes. We rely on Principal Stratification to formulate a relaxed version of SI: Latent Sequential Ignorability (LSI) assumes that treatment assignment is conditionally independent on future potential outcomes given past treatments, covariates and principal stratum membership, a latent variable defined by the joint value of observed and missing intermediate outcomes. We evaluate SI and LSI, using theoretical arguments and simulation studies to investigate the performance of the two assumptions when one holds and inference is conducted under both. Simulations show that when SI does not hold, inference performed under SI leads to misleading conclusions. Conversely, LSI generally leads to correct posterior distributions, irrespective of which assumption holds.

Type: Article
Title: Bayesian Inference for Sequential Treatments under Latent Sequential Ignorability
Open access status: An open access version is available from UCL Discovery
DOI: 10.1080/01621459.2019.1623039
Publisher version: https://doi.org/10.1080/01621459.2019.1623039
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Longitudinal treatments, Principal stratification, Rubin causal model, Sequential ignorablity
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Statistical Science
URI: https://discovery.ucl.ac.uk/id/eprint/10056182
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