2022 Winter

Date: 2022-04-08 Time: 15:35-16:35 (Montreal time) https://mcgill.zoom.us/j/83436686293?pwd=b0RmWmlXRXE3OWR6NlNIcWF5d0dJQT09 Meeting ID: 834 3668 6293 Passcode: 12345 Abstract: High dimensional data are rapidly growing in many domains, for example, in microarray gene expression studies, fMRI data analysis, large-scale healthcare analytics, text/image analysis, natural language processing and astronomy, to name but a few. In the last two decades regularisation approaches have become the methods of choice for analysing high dimensional data. However, obtaining accurate estimates and predictions as well as valid statistical inference remains a major challenge in high dimensional situations.

Date: 2022-04-01 Time: 15:35-16:35 (Montreal time) https://mcgill.zoom.us/j/83436686293?pwd=b0RmWmlXRXE3OWR6NlNIcWF5d0dJQT09 Meeting ID: 834 3668 6293 Passcode: 12345 Abstract: We introduce Learn then Test, a framework for calibrating machine learning models so that their predictions satisfy explicit, finite-sample statistical guarantees regardless of the underlying model and (unknown) data-generating distribution. The framework addresses, among other examples, false discovery rate control in multi-label classification, intersection-over-union control in instance segmentation, and the simultaneous control of the type-1 error of outlier detection and confidence set coverage in classification or regression.

Date: 2022-03-25 Time: 15:35-16:35 (Montreal time) https://mcgill.zoom.us/j/83436686293?pwd=b0RmWmlXRXE3OWR6NlNIcWF5d0dJQT09 Meeting ID: 834 3668 6293 Passcode: 12345 Abstract: In data analysis problems where we are not able to rely on distributional assumptions, what types of inference guarantees can still be obtained? Many popular methods, such as holdout methods, cross-validation methods, and conformal prediction, are able to provide distribution-free guarantees for predictive inference, but the problem of providing inference for the underlying regression function (for example, inference on the conditional mean E[Y|X]) is more challenging.

Date: 2022-03-11 Time: 15:30-16:30 (Montreal time) https://mcgill.zoom.us/j/83436686293?pwd=b0RmWmlXRXE3OWR6NlNIcWF5d0dJQT09 Meeting ID: 834 3668 6293 Passcode: 12345 Abstract: Finding the optimal treatment regime (or a series of sequential treatment regimes) based on individual characteristics has important applications in precision medicine. We propose two new approaches to quantify uncertainty in optimal treatment regime estimation. First, we consider inference in the model-free setting, which does not require specifying an outcome regression model. Existing model-free estimators for optimal treatment regimes are usually not suitable for the purpose of inference, because they either have nonstandard asymptotic distributions or do not necessarily guarantee consistent estimation of the parameter indexing the Bayes rule due to the use of surrogate loss.

Date: 2022-02-18 Time: 15:30-16:30 (Montreal time) https://umontreal.zoom.us/j/85105423917?pwd=enM3MGpFNkZKU2daMjRITmo0N0JUUT09 Meeting ID: 851 0542 3917 Passcode: 403790 Abstract: Extremal graphical models are sparse statistical models for multivariate extreme events. The underlying graph encodes conditional independencies and enables a visual interpretation of the complex extremal dependence structure. For the important case of tree models, we provide a data-driven methodology for learning the graphical structure. We show that sample versions of the extremal correlation and a new summary statistic, which we call the extremal variogram, can be used as weights for a minimum spanning tree to consistently recover the true underlying tree.

Date: 2022-02-11 Time: 15:30-16:30 (Montreal time) https://mcgill.zoom.us/j/83436686293?pwd=b0RmWmlXRXE3OWR6NlNIcWF5d0dJQT09 Meeting ID: 834 3668 6293 Passcode: 12345 Abstract: The cellular states in various biological processes such as cell differentiation, disease progression, and treatment response are often enormously complex and thus hard to be profiled with unimodal profiling (e.g., transcriptome). Although those unimodal measurements had brought success for studies in a large variety of studies, the incomplete (and often misleading) unimodal cellular profiling could lead to biased and inaccurate conclusions.

Date: 2022-02-04 Time: 15:30-16:30 (Montreal time) https://mcgill.zoom.us/j/83436686293?pwd=b0RmWmlXRXE3OWR6NlNIcWF5d0dJQT09 Meeting ID: 834 3668 6293 Passcode: 12345 Abstract: In this talk, we consider constructing a confidence interval for a target policy’s value offline based on pre-collected observational data in infinite horizon settings. Most of the existing works assume no unmeasured variables exist that confound the observed actions. This assumption, however, is likely to be violated in real applications such as healthcare and technological industries.

Date: 2022-01-28 Time: 15:30-16:30 (Montreal time) https://umontreal.zoom.us/j/93983313215?pwd=clB6cUNsSjAvRmFMME1PblhkTUtsQT09 Meeting ID: 939 8331 3215 Passcode: 096952 Abstract: Statistical risk assessment, in particular in finance and insurance, requires estimating simple indicators to summarize the risk incurred in a given situation. Of most interest is to infer extreme levels of risk so as to be able to manage high-impact rare events such as extreme climate episodes or stock market crashes. A standard procedure in this context, whether in the academic, industrial or regulatory circles, is to estimate a well-chosen single quantile (or Value-at-Risk).

Date: 2022-01-21 Time: 15:30-16:30 (Montreal time) https://mcgill.zoom.us/j/83436686293?pwd=b0RmWmlXRXE3OWR6NlNIcWF5d0dJQT09 Meeting ID: 834 3668 6293 Passcode: 12345 Abstract: The change-point analysis is more than sixty years old. Over this long period, it has been an important subject of interest in many scientific disciplines such as finance and econometrics, bioinformatics and genomics, climatology, engineering, and technology. In this talk, I will provide a general overview of the topic alongside some historical notes. I will then review the most recent and transformative advancements on the subject.