Levin Lecture Series: Fall 2018 Colloquium Seminars

September 13, 2018

Topic: "Robust regression with compositional covariates"

Speaker: Aditya Mishra, Research Fellow, Flatiron Institute's Center for Computational Biology

11:45am-12:45pm​

AR Building, 8th Floor Auditorium

Hosted by: Dr. Ian McKeague

Abstract: Recent advances in low-cost metagenomic and amplicon sequencing techniques enable routine sampling of environmental and host-associated microbial communities across different habitats. The data produced by these large-scale surveys typically comprise relative abundances (or compositions) of microbial taxa at different taxonomic levels. To investigate the dependency of additional covariate measurements such as metabolites or host phenotypes on the microbial compositions we introduce a general robust regression framework for compositional data. We propose a novel log-contrast regression model with mean shift parameters that allows the identification of sample outliers and maintains sub-compositional coherence with respect to the associated phylogenetic tree. The model is estimated using a sparse penalized regression approach that simultaneously enforces sparsity in mean shift and covariate parameters. We demonstrate the superiority of our approach using a wide range of synthetic simulation scenarios and infer novel associations between body mass index measurements and human gut microbes on a large public collection of human gut microbiome data.

 

September 20, 2018

Topic: "Quantitation in Colocalization Analysis: Beyond "Red + Yellow = Green"

Speaker: Ming Yuan, Professor, Department of Statistics, Columbia University

11:45am-12:45pm​

AR Building, 8th Floor Auditorium

Hosted by: Dr. Bin Cheng

Abstract: "I see yellow; therefore, there is colocalization.”  Is it really so simple when it comes to colocalization studies?  Unfortunately, and fortunately, no.  Colocalization is in fact a supremely powerful technique for scientists who want to take full advantage of what optical microscopy has to offer: quantitative, correlative information together with spatial resolution. Yet, methods for colocalization have been put into doubt now that images are no longer considered simple visual representations.  Colocalization studies have notoriously been subject to misinterpretation due to difficulties in robust quantification and, more importantly, reproducibility, which results in a constant source of confusion, frustration, and error. In this talk, I will share some of our effort and progress to ease such challenges using novel statistical and computational tools.

 

September 27, 2018 

Topic: "Integrative Directed Cyclic Graphical Models with Heterogeneous Samples”​

Speaker: Alex Dmitrienko, Founder and President, Mediana Inc.

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Naitee Ting

Abstract: This presentation will provide an overview of multiplicity issues arising in confirmatory clinical trials and introduce a general framework for constructing multiple testing procedures (MTPs) for trials with hierarchical objectives (also known as gatekeeping procedures).  Multiplicity problems with hierarchical objectives frequently exhibit a complex structure, including multiple families of hypotheses (based on several clinical endpoints, dose-control comparisons, patient populations, etc) and logical restrictions.  The proposed mixture-based approach relies on combining multiple tests across families and supports powerful and flexible MTPs, e.g., multi-stage procedures based on Hochberg-type tests that account for logical restrictions among the hypotheses of interest.  Clinical trial examples with traditional and adaptive designs will be used to illustrate the mixture-based approach and software implementation of mixture-based gatekeeping procedures will be discussed.

 

October 4, 2018

Topic: "Interval Dose-Finding Designs: From Model-Based to Model-Free?"

Speaker:  Yuan Ji, Professor, Department of Public Health Sciences, The University of Chicago

11:45am-12:45pm​

AR Building, 8th Floor Auditorium

Hosted by: Dr. Codruta Chiuzan

Abstract: In this talk, I will introduce a set of interval dose-finding designs, including the mTPI, mTPI-2, BOIN, and Keyboard designs. I will provide a theoretical and practical overview of these methods, their frequentist performance, and the pros and cons when compared to standard designs such as 3+3. Model-based designs such as CRM and BLRM will also be discussed. Finally, a new design, called the i3+3 design will be introduced, which is completely model-free. The i3+3 design stands for the interval 3+3 design, which uses a set of simple rules for dose escalation. The performance of the i3+3 design is compared with the interval designs, the 3+3 design, and the CRM and BLRM designs. A new metric to summarize the operating characteristics into a single value is used to evaluate all the designs.

 

October 11, 2018

Topic: "Geometric methods for image-based statistical analysis of brain tumors​"

Speaker:  Sebastian Kurtek, Associate Professor, Department of Statistics, Ohio State University

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Todd Ogden

Abstract: Biomedical studies are a common source of rich and complex imaging data. The statistical analysis of such datasets requires novel methodological developments due to two main challenges: (1) the functional nature of the data objects under study, and (2) the nonlinearity of their representation spaces. In this work, we consider the task of quantifying and analyzing two different types of tumor heterogeneity. The first type, which is represented by a probability density function, summarizes the tumor’s texture information. We use the nonparametric Fisher-Rao Riemannian framework to develop intrinsic statistical methods on the space of probability density functions for summarization and inference. The second type, which is represented by a parameterized, planar closed curve, captures the tumor’s shape information. A key component of analyzing tumor shapes is a suitable metric that enables efficient comparisons, provides tools for computing descriptive statistics and implementing principal component analysis on the tumor shape space, and allows for a rich class of continuous deformations of tumor shape. We demonstrate the utility of our framework on a dataset of Magnetic Resonance Images of patients diagnosed with Glioblastoma Multiforme, a malignant brain tumor with poor prognosis. This work was done in collaboration with my PhD student Abhijoy Saha, as well as colleagues Karthik Bharath (University of Nottingham), Veera Baladandayuthapani (University of Michigan) and Arvind Rao (University of Michigan).

 

October 18, 2018

Topic: "Scalable and Model-free Methods for Multiclass Probability Estimation"

Speaker:  Helen Zhang, Professor, Department of Mathematics, University of Arizona

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Seonjoo Lee

Abstract: Classical approaches for multiclass probability estimation are mostly model-based, such as logistic regression or LDA, by making certain assumptions on the underlying data distribution. We propose a new class of model-free methods to estimate class probabilities based on large-margin classifiers. The method is scalable for high-dimensional data by employing the divide-and-conquer technique, which solves multiple weighted large-margin classifiers and then constructs probability estimates by aggregating multiple classification rules. Without relying on any parametric assumption, the estimates are shown to be consistent asymptotically. Both simulated and real data examples are presented to illustrate performance of the new procedure.

This is the joint work with Xin Wang and Yichao Wu.

 

October 25, 2018

Topic: "TBA"

Speaker:  Yu Shyr, Professor and Chair, Department of Biostatistics, Vanderbilt University

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Shing Lee

Abstract: "TBA"

 

November 1, 2018

Topic: "TBA"

Speaker:  Fei Zou, Professor, Department of Biostatistics, University of North Carolina at Chapel Hill

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Jianhua Hu

Abstract: "TBA"

 

November 15, 2018

Topic: "TBA"

Speaker:  Debashis Ghosh, Professor and Chair, Department of Biostatistics and Informatics, Colorado School of Public Health

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Gen Li

Abstract: "TBA"

 

November 29, 2018

Topic: "TBA"

Speaker:  Michael Wu, Associate Member, Public Health Sciences Division, Fred Hutch Cancer Research Center

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Iuliana Ionita-Laza

Abstract: "TBA"

 

December 6, 2018

Topic: "TBA"

Speaker:  Joseph Sedransk, Professor, Joint Program in Survey Methodology, University of Maryland

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Qixuan Chen

Abstract: "TBA"

 

December 13, 2018

Topic: "TBA"

Speaker:  Peisong Han, Assistant Professor, Department of Biostatistics, University of Michigan

11:45am-12:45pm

AR Building, 8th Floor Auditorium

Hosted by: Dr. Zhezhen Jin

Abstract: "TBA"