arXiv subjects

Mengqi Lin

Publications and source records attributed to Mengqi Lin.

3 recordsLinked to original sources

arXiv2026

Stochastic Sensitivity Analysis for Matched Observational Studies

Sensitivity analysis asks how strong unmeasured confounding needs to be to explain away an observational study's conclusion. The conventional approach in matched studies conducts inference conditional upon the potential outcomes as well as both observed and unobserved confounders, and then finds the worst-case distribution for the conditional treatment assignments across all possible realizations of the unobserved confounder. The resulting worst-case allocation imagines strong, near perfect, correlations between the potential outcomes and hidden bias. We propose a stochastic sensitivity analysis that instead targets inference conditional upon potential outcomes and observed confounders while treating the hidden confounders as random with unknown conditional laws. Rather than finding the worst-case realizations for the hidden confounders, we instead determine the worst-case conditional law over a broad class of distributions. This preserves the adversarial spirit of sensitivity analysis while allowing for imperfect alignment between hidden bias and potential outcomes to a degree controlled by a scalar sensitivity parameter. We consider restrictions to both an interpretable class with no parametric assumptions and a Bernoulli class of conditional laws. Design sensitivity calculations and real-data demonstrations illustrate that allowing for even a small degree of stochasticity can materially increase reported robustness to hidden bias relative to the conventional approach.

stat.ME↗

arXiv2025

Simultaneous Inference for False Discovery Proportions under Sensitivity Models for Observational Studies

We provide an approach to exploratory data analysis in observational studies with a single intervention and multiple endpoints. In such settings, the researcher would like to explore evidence for actual treatment effects while accounting for both false discoveries and the potential impact of unmeasured confounding. For any candidate subset of hypotheses about these outcomes, we provide sensitivity sets for the proportion of the hypotheses within the subset which are true. The resulting sensitivity statements are valid simultaneously over all possible choices for the rejected set, allowing the researcher to search for promising subsets of hypotheses that maintain a large estimated fraction of true discoveries even if hidden bias is present. The approach is well suited to sensitivity analysis, as conclusions that some fraction of outcomes are affected by the treatment exhibit larger robustness to unmeasured confounding than findings that any particular outcome is affected. For Rosenbaum's sensitivity model in matched observational studies, we show how a sequence of integer programs, in tandem with screening steps, facilitate the efficient computation of the required sensitivity sets. We illustrate the practical utility of our method through both simulation studies and a data example on the long-term impacts of childhood abuse.

stat.ME↗

arXiv2023

Sufficient and Necessary Conditions for the Identifiability of DINA Models with Polytomous Responses

Cognitive Diagnosis Models (CDMs) provide a powerful statistical and psychometric tool for researchers and practitioners to learn fine-grained diagnostic information about respondents' latent attributes. There has been a growing interest in the use of CDMs for polytomous response data, as more and more items with multiple response options become widely used. Similar to many latent variable models, the identifiability of CDMs is critical for accurate parameter estimation and valid statistical inference. However, the existing identifiability results are primarily focused on binary response models and have not adequately addressed the identifiability of CDMs with polytomous responses. This paper addresses this gap by presenting sufficient and necessary conditions for the identifiability of the widely used DINA model with polytomous responses, with the aim to provide a comprehensive understanding of the identifiability of CDMs with polytomous responses and to inform future research in this field.

stat.ME↗