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Semiparametric Inference of the Complier Average Causal Effect with Nonignorable Missing Outcomes

Published: 03 December 2015 Publication History

Abstract

Noncompliance and missing data often occur in randomized trials, which complicate the inference of causal effects. When both noncompliance and missing data are present, previous papers proposed moment and maximum likelihood estimators for binary and normally distributed continuous outcomes under the latent ignorable missing data mechanism. However, the latent ignorable missing data mechanism may be violated in practice, because the missing data mechanism may depend directly on the missing outcome itself. Under noncompliance and an outcome-dependent nonignorable missing data mechanism, previous studies showed the identifiability of complier average causal effect for discrete outcomes. In this article, we study the semiparametric identifiability and estimation of complier average causal effect in randomized clinical trials with both all-or-none noncompliance and outcome-dependent nonignorable missing continuous outcomes, and propose a two-step maximum likelihood estimator in order to eliminate the infinite dimensional nuisance parameter. Our method does not need to specify a parametric form for the missing data mechanism. We also evaluate the finite sample property of our method via extensive simulation studies and sensitivity analysis, with an application to a double-blinded psychiatric clinical trial.

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    Published In

    cover image ACM Transactions on Intelligent Systems and Technology
    ACM Transactions on Intelligent Systems and Technology  Volume 7, Issue 2
    Special Issue on Causal Discovery and Inference
    January 2016
    270 pages
    ISSN:2157-6904
    EISSN:2157-6912
    DOI:10.1145/2850424
    • Editor:
    • Yu Zheng
    Issue’s Table of Contents
    Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from [email protected]

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    Publication History

    Published: 03 December 2015
    Accepted: 01 September 2014
    Revised: 01 June 2014
    Received: 01 March 2014
    Published in TIST Volume 7, Issue 2

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    Author Tags

    1. Causal inference
    2. instrumental variable
    3. missing not at random
    4. noncompliance
    5. outcome-dependent missing
    6. principal stratification

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