Jiajun Liu

Preprint · November 18, 2025 The area under the ROC curve (AUC) is the standard measure of a biomarker's discriminatory accuracy; however, AUC is rarely treated as a population-specific estimand. When validation cohorts differ from the intended target population in case mix, Naïve AUC ... Link to item Cite

Variance Estimation for Weighted Average Treatment Effects.

Journal article Stat Biosci · September 15, 2025 Common variance estimation methods for weighted average treatment effects (WATEs) in observational studies include nonparametric bootstrap and model-based, closed-form sandwich variance estimation. However, the computational cost of bootstrap increases wit ... Full text Open Access Link to item Cite

Variance Estimation for Weighted Average Treatment Effects

Preprint · August 11, 2025 Common variance estimation methods for weighted average treatment effects (WATEs) in observational studies include nonparametric bootstrap and model-based, closed-form sandwich variance estimation. However, the computational cost of bootstrap increases wit ... Link to item Cite

Robust Estimation and Inference in Hybrid Controlled Trials for Binary Outcomes: A Case Study on Non-Small Cell Lung Cancer

Preprint · April 30, 2025 Hybrid controlled trials (HCTs), which augment randomized controlled trials (RCTs) with external controls (ECs), are increasingly receiving attention as a way to address limited power, slow accrual, and ethical concerns in clinical research. However, borro ... Link to item Cite

Assessing racial disparities in healthcare expenditure using generalized propensity score weighting.

Journal article BMC Med Res Methodol · March 7, 2025 PURPOSE: This paper extends current propensity score weighting methods for causal inference to better understand disparities in healthcare access across multiple racial groups. By treating each racial group as a distinct entity (or "treatment") in the caus ... Full text Open Access Link to item Cite

Covariate Adjustment in Analyzing Randomized Clinical Trials: Approaches, Software, and Application

Book section · November 1, 2024 This book aims to booster research, education, and training in biostatistics and in biopharmaceutical research and development. ... Open Access Cite

Statistical Evaluation of Responder Analysis in Stem Cell Clinical Trials.

Journal article Ther Innov Regul Sci · November 2023 BACKGROUND: In evaluating treatment efficacy, there is an ongoing discussion about which endpoint is more efficient to represent the treatment effect. Absolute change (AC) is the difference between before and after treatment, while relative change (RC) is ... Full text Link to item Cite

A Proposal for Post Hoc Subgroup Analysis in Support of Regulatory Submission.

Journal article Ther Innov Regul Sci · March 2023 BACKGROUND: In clinical trials, it is not uncommon that the primary analysis fails to achieve the study objective for demonstrating the safety and efficacy of a test treatment under investigation, while a specific sub-population analysis shows a significan ... Full text Open Access Link to item Cite