Reliable Causal Inference
Causal conclusions can fail when instruments are weak or invalid, treatment assignment is endogenous, or important confounders are unobserved. My work develops identification strategies, tests, and estimators for causal effects that remain reliable under these departures, with particular emphasis on instrumental variables, heterogeneous treatment effects, mediation, and observational-study design.
Related work 24
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Mei, Z., Fan, Q., and Guo, Z. (2026).
Identification and Robust Inference for Multiple Treatment Effects with Possibly Invalid Instruments.
Technical Report
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Heng, S.#✉, Shen, Y.#, Guo, Z.✉ (2026).
Propensity Score Propagation: A General Framework for Design-Based Inference with Unknown Propensity Scores.
Technical Report
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Chang, T. H., Guo, Z., and Malinsky, D. (2026).
Post-selection inference for causal effects after causal discovery.
Biometrika, 113(1), asaf073.
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Guo, Z., Zheng, M., and Bühlmann, P. (2026).
Robustness Against Weak or Invalid Instruments: Exploring Nonlinear Treatment Models with Machine Learning
Journal of Machine Learning Research, to appear.
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Scheidegger, C., Guo, Z., and Bühlmann, P. (2026).
Inference for Heterogeneous Treatment Effects with Efficient Instruments and Machine Learning
Electronic Journal of Statistics, 20(1), 718–770.
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Koo, T. and Guo, Z. (2025).
Distributionally Robust Synthetic Control: Ensuring Robustness Against Highly Correlated Controls and Weight Shifts.
Technical Report
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Zheng, M., Bonvini, M.✉, and Guo, Z.✉ (2025).
Perturbed Double Machine Learning: Nonstandard Inference Beyond the Parametric Length
Technical Report
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Gu, Y., Fang, C., Xu, Y., Guo, Z., and Fan, J. (2025).
Fundamental Computational Limits in Pursuing Invariant Causal Prediction and Invariance-Guided Regularization
Technical Report
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Scheidegger, C., Guo, Z., and Bühlmann, P. (2025).
Spectral deconfounding for high-dimensional sparse additive models
ACM/IMS Journal of Data Science, 2(1), Article 1, 52 pages.
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*Fan, Q., Guo, Z., and Mei, Z. (2025).
A Heteroscedasticity-Robust Overidentifying Restriction Test with High-Dimensional Covariates
Journal of Business & Economic Statistics, 43(2), 413-422.
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Carl, D., Emmenegger, C., Bühlmann, P., and Guo, Z. (2025).
TSCI: Two Stage Curvature Identification for Causal Inference with Invalid Instruments in R
Journal of Statistical Software, 114(7), 1-21. [Code]
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Kang, H., Guo, Z., Liu, Z., and Small, D. (2025).
Identification and Inference with Invalid Instruments
Annual Review of Statistics and Its Application, 12, 385–405.
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Wang, Z.#, Hu, Y.#, Bühlmann, P.✉, and Guo, Z.✉ (2024).
Causal Invariance Learning via Efficient Nonconvex Optimization
Technical Report
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Zhu, J., Zhang, J., Guo, Z., and Heng, S. (2023).
Randomization-Based Inference for Average Treatment Effects in Inexactly Matched Observational Studies.
Technical Report
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*Fan, Q., Guo, Z., Mei, Z., and Zhang, C. (2023).
Inference for Nonlinear Endogenous Treatment Effects Accounting for High-Dimensional Covariate Complexity.
Technical report
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Guo, Z. (2023).
Causal Inference with Invalid Instruments: Post-selection Problems and A Solution Using Searching and Sampling.
Journal of the Royal Statistical Society: Series B (Statistical Methodology), 85(3), 959-985. [Code]
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Koo, T., Lee, Y., Small, D., Guo, Z. (2023).
RobustIV and controlfunctionIV: Causal Inference for Linear and Nonlinear Models with Invalid Instrumental Variables
Observational Studies, 9(4), 97-120. [Code]
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Guo, Z.#✉, Ćevid, D.#, and Bühlmann, P. (2022).
Doubly Debiased Lasso: High-Dimensional Inference under Hidden Confounding.
Annals of Statistics, 50 (3), 1320 - 1347. [Code]
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Guo, Z., Kang, H., Cai, T. T. and Small, D. S. (2018).
Testing Endogeneity with High Dimensional Covariates.
The Journal of Econometrics, 207(1), 175-187. [Code]
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Guo, Z., Kang, H., Cai, T. T. and Small, D. S. (2018).
Confidence Intervals for Causal Effects with Invalid Instruments using Two-Stage Hard Thresholding with Voting.
Journal of the Royal Statistical Society: Series B, 80(4), 793-815. [Code]
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Guo, Z., Small, D. S., Gansky, S. A., and Cheng, J. (2018).
Mediation Analysis for Count and Zero-Inflated Count Data without Sequential Ignorability.
Journal of the Royal Statistical Society: Series C, 67(2), 371-394. [Code]
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Cheng J., Cheng, N. F., Guo, Z., Gregorich, S., Ismail, A. I. and Gansky, S. A. (2018).
Mediation Analysis for Count and Zero-Inflated Count Data.
Statistical Methods in Medical Research, 27(9), 2756-2774. [Code]
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Guo, Z. and Small, D. S. (2016).
Control Function Instrumental Variable Estimation of Nonlinear Causal Effect Models.
Journal of Machine Learning Research, 17(100):1-35, 2016. [Code]
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Guo, Z., Cheng, J., Lorch, S. A., and Small, D. S. (2014).
Using an Instrumental Variable to Test for Unmeasured Confounding.
Statistics in Medicine, 33, 3528 - 3546. [Code]