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In this work, we study the sample complexity problem of risk-sensitive Reinforcement Learning (RL) with a generative model, where we aim to maximize the Conditional Value at Risk (CVaR) with risk tolerance level $\tau$ at each step, a…

Machine Learning · Computer Science 2025-03-25 Zilong Deng , Simon Khan , Shaofeng Zou

We introduce a new method for estimating the mean of an outcome variable within groups when researchers only observe the average of the outcome and group indicators across a set of aggregation units, such as geographical areas. Existing…

Methodology · Statistics 2026-05-01 Cory McCartan , Shiro Kuriwaki

In recent years, data selection has emerged as a core issue for large-scale visual-language model pretraining, especially on noisy web-curated datasets. One widely adopted strategy assigns quality scores such as CLIP similarity for each…

Machine Learning · Computer Science 2024-02-06 Yiping Wang , Yifang Chen , Wendan Yan , Kevin Jamieson , Simon Shaolei Du

We introduce a novel covariance estimator for portfolio selection that adapts to the non-stationary or persistent heteroskedastic environments of financial time series by employing exponentially weighted averages and nonlinearly shrinking…

Machine Learning · Statistics 2023-01-23 Vincent Tan , Stefan Zohren

In mesh simplification, common requirements like accuracy, triangle quality, and feature alignment are often considered as a trade-off. Existing algorithms concentrate on just one or a few specific aspects of these requirements. For…

Fine stratification survey is useful in many applications as its point estimator is unbiased, but the variance estimator under the design cannot be easily obtained, particularly when the sample size per stratum is as small as one unit. One…

Methodology · Statistics 2026-03-05 Sepideh Mosaferi , Shonosuke Sugasawa

First, we analyze the variance of the Cross Validation (CV)-based estimators used for estimating the performance of classification rules. Second, we propose a novel estimator to estimate this variance using the Influence Function (IF)…

Machine Learning · Statistics 2021-11-10 Waleed A. Yousef

There is currently an increasing interest in large vector autoregressive (VAR) models. VARs are popular tools for macroeconomic forecasting and use of larger models has been demonstrated to often improve the forecasting ability compared to…

Econometrics · Economics 2019-07-03 Sebastian Ankargren , Paulina Jonéus

We consider estimation of a multivariate normal mean vector under sum of squared error loss. We propose a new class of smooth estimators parameterized by \alpha dominating the James-Stein estimator. The estimator for \alpha=1 corresponds to…

Statistics Theory · Mathematics 2010-09-14 Yuzo Maruyama

We propose a non-asymptotic convergence analysis of a two-step approach to learn a conditional value-at-risk (VaR) and a conditional expected shortfall (ES) using Rademacher bounds, in a non-parametric setup allowing for heavy-tails on the…

Computational Finance · Quantitative Finance 2024-09-20 D Barrera , S Crépey , E Gobet , Hoang-Dung Nguyen , B Saadeddine

Distributional reinforcement learning (RL) -- in which agents learn about all the possible long-term consequences of their actions, and not just the expected value -- is of great recent interest. One of the most important affordances of a…

Artificial Intelligence · Computer Science 2021-11-15 Chris Gagne , Peter Dayan

CVaR (Conditional Value at Risk) is a risk metric widely used in finance. However, dynamically optimizing CVaR is difficult since it is not a standard Markov decision process (MDP) and the principle of dynamic programming fails. In this…

Optimization and Control · Mathematics 2022-10-18 Li Xia , Peter W. Glynn

Maximum likelihood estimation of large Markov-switching vector autoregressions (MS-VARs) can be challenging or infeasible due to parameter proliferation. To accommodate situations where dimensionality may be of comparable order to or…

Econometrics · Economics 2021-07-28 Kenwin Maung

Precise quantum expectation values are crucial for quantum algorithm development, but noise in real-world systems can degrade these estimations. While quantum error correction is resource-intensive, error mitigation strategies offer a…

Quantum Physics · Physics 2025-01-31 Touheed Anwar Atif , Reuben Blake Tate , Stephan Eidenbenz

We study risk-sensitive planning under partial observability using the dynamic risk measure Iterated Conditional Value-at-Risk (ICVaR). A policy evaluation algorithm for ICVaR is developed with finite-time performance guarantees that do not…

Artificial Intelligence · Computer Science 2026-01-29 Yaacov Pariente , Vadim Indelman

We tackle covariance estimation in low-sample scenarios, employing a structured covariance matrix with shrinkage methods. These involve convexly combining a low-bias/high-variance empirical estimate with a biased regularization estimator,…

Instrumentation and Methods for Astrophysics · Physics 2024-06-28 Olivier Flasseur , Eric Thiébaut , Loïc Denis , Maud Langlois

Robust Markov Decision Processes (RMDPs) have received significant research interest, offering an alternative to standard Markov Decision Processes (MDPs) that often assume fixed transition probabilities. RMDPs address this by optimizing…

Machine Learning · Computer Science 2024-05-06 Xinyi Ni , Lifeng Lai

Robust estimators for linear regression require non-convex objective functions to shield against adverse affects of outliers. This non-convexity brings challenges, particularly when combined with penalization in high-dimensional settings.…

Computation · Statistics 2025-08-08 David Kepplinger , Siqi Wei

The semiparametric accelerated failure time model is not as widely used as the Cox relative risk model mainly due to computational difficulties. Recent developments in least squares estimation and induced smoothing estimating equations…

Methodology · Statistics 2015-06-02 Steven Chiou , Junghi Kim , Jun Yan

Empirical Bayes estimators are based on minimizing the average risk with the hyper-parameters in the weighting function being estimated from observed data. The performance of an empirical Bayes estimator is typically evaluated by its mean…

Statistics Theory · Mathematics 2025-03-18 Yue Ju , Bo Wahlberg , Håkan Hjalmarsson