Statistics and Probability Commons^™

On The Restricted Mean Event Time In Survival Analysis, Lu Tian, Lihui Zhao, L. J. Wei

Harvard University Biostatistics Working Paper Series

No abstract provided.

Surrogacy Assessment Using Principal Stratification When Surrogate And Outcome Measures Are Multivariate Normal, Anna Conlon, Jeremy M.G. Taylor, Michael R. Elliott

The University of Michigan Department of Biostatistics Working Paper Series

No abstract provided.

Lifetime Musical Activities And Cognitive Function Of The Elderly, Alicia Nevriana, Pandu Riono, Tri Budi W. Rahardjo, Adji Kusumadjati

Kesmas

Penurunan fungsi kognitif merupakan salah satu masalah umum pada lanjut usia yang mampu memengaruhi kualitas hidup mereka. Musik merupakan sebuah elemen yang dipercaya mampu berkontribusi terhadap kualitas hidup mereka. Meski demikian, hubungan antara aktivitas musikal yang dilakukan sepanjang hidup dan fungsi kognitif lansia belum diketahui secara pasti. Pada penelitian ini, hubungan antara aktivitas musikal sepanjang hidup dan fungsi kognitif dievaluasi. Lima puluh tiga lansia penghuni panti tresna werdha di Jakarta Timur dipilih dan diwawancarai terkait karakteristik dan aktivitas musikal sepanjang hidup mereka. Fungsi kognitif juga diukur menggunakan MMSE. Hasil penelitian ini menunjukkan adanya kemungkinan asosiasi antara aktivitas musikal sepanjang hidup …

Targeted Estimation Of Variable Importance Measures With Interval-Censored Outcomes, Stephanie Sapp, Mark J. Van Der Laan, Kimberly Page

U.C. Berkeley Division of Biostatistics Working Paper Series

In most experimental and observational studies, participants are not followed in continuous time. Instead, data is collected about participants only at certain monitoring times. These monitoring times are random, and often participant specific. As a result, outcomes are only known up to random time intervals, resulting in interval-censored data. In contrast, when estimating variable importance measures on interval-censored outcomes, practitioners often ignore the presence of interval-censoring, and instead treat the data as continuous or right-censored, applying ad-hoc approaches to mask the true interval-censoring. In this paper, we describe Targeted Minimum Loss-based Estimation methods tailored for estimation of variable importance measures …

Observational Intensity Bias Associated With Illness Adjustment: Cross Sectional Analysis Of Insurance Claims, J. E. Wennberg, D. O. Staiger, S. M. Sharp, D. J. Gottlieb

Dartmouth Scholarship

Objective: To determine the bias associated with frequency of visits by physicians in adjusting for illness, using diagnoses recorded in administrative databases.

Setting: Claims data from the US Medicare program for services provided in 2007 among 306 US hospital referral regions.

Design: Cross sectional analysis. Participants 20% sample of fee for service Medicare beneficiaries residing in the United States in 2007 (n=5 153 877).

Progress Realized: Trends In Hiv-1 Viral Load And Cd4 Cell Count In A Tertiary-Care Center From 1999 Through 2011, Howard B. Gale, Manuel D. Rodriguez, Heather J. Hoffman, Debra A. Benator, Fred M. Gordin, Ann M. Labriola, Virginia L. Kan

Epidemiology Faculty Publications

Abstract

Accumulating evidence suggests that alterations in immune function may be important in the etiology of papillary thyroid cancer (PTC). To identify genetic markers in immune-related pathways, we evaluated 3,985 tag single nucleotide polymorphisms (SNPs) in 230 candidate gene regions (adhesion-extravasation-migration, arachidonic acid metabolism/eicosanoid signaling, complement and coagulation cascade, cytokine signaling, innate pathogen detection and antimicrobials, leukocyte signaling, TNF/NF-kB pathway or other) in a case-control study of 344 PTC cases and 452 controls. We used logistic regression models to estimate odds ratios (OR) and calculate one degree of freedom P values of linear trend (PSNP-trend) for the association …

Sensor Calibration Systems And Methods For Infrared Cameras, George Speake, Nuwan Nagahawatte, Richard M. Goeden, Ted Takagi, Robert Ernst, Gary B. Hughes, Joseph Kostrzewa, John Graff, Russell Granneman, Michael Kent, Neela Nalam, Stephen Lyon, Barbara Sharp, Pierre Boulanger, Neil Cuteliffe, Tim Martin, Ted Hoelter

Statistics

Systems and methods directed to calibration techniques for infrared cameras are disclosed for some embodiments. For example, a method of determining infrared sensor calibration information, in accordance with an embodiment, includes performing a calibration operation on an infrared sensor to obtain calibration information, wherein the infrared sensor is not within an infrared camera core, and storing the calibration information.

Influenza Forecasting With Google Flu Trends, Andrea Freyer Dugas, Mehdi Jalalpour, Yulia Gel, Scott Levin, Fred Torcaso, Takeru Igusa, Richard E. Rothman

Civil and Environmental Engineering Faculty Publications

Background: We developed a practical influenza forecast model based on real-time, geographically focused, and easy to access data, designed to provide individual medical centers with advanced warning of the expected number of influenza cases, thus allowing for sufficient time to implement interventions. Secondly, we evaluated the effects of incorporating a real-time influenza surveillance system, Google Flu Trends, and meteorological and temporal information on forecast accuracy.

Methods: Forecast models designed to predict one week in advance were developed from weekly counts of confirmed influenza cases over seven seasons (2004–2011) divided into seven training and out-of-sample verification sets. Forecasting procedures …

Location And Capacity Modeling Of Network Interchanges, Aldo D. Fabregas

USF Tampa Graduate Theses and Dissertations

Network design decisions, especially those pertaining to urban infrastructure, are made by a central authority or network leader, and taking into consideration the network users or followers. These network decision problems are formulated as non-linear bi-level programming problems. In this work, a continuous network design problem (CNDP) and discrete network design problem (DNDP) bi-level optimization programs are proposed and solved in the context of transportation planning. The solution strategy involved reformulation and linearization as a single-level program by introducing the optimality conditions of the lower level problem into the upper level problem. For the CNDP, an alternative linearization algorithm (modified …

Missing At Random And Ignorability For Inferences About Subsets Of Parameters With Missing Data, Roderick J. Little, Sahar Zanganeh

The University of Michigan Department of Biostatistics Working Paper Series

For likelihood-based inferences from data with missing values, Rubin (1976) showed that the missing data mechanism can be ignored when (a) the missing data are missing at random (MAR), in the sense that missingness does not depend on the missing values after conditioning on the observed data, and (b) the parameters of the data model and the missing-data mechanism are distinct; that is, there are no a priori ties, via parameter space restrictions or prior distributions, between the parameters of the data model and the parameters of the model for the mechanism. Rubin described (a) and (b) as the "weakest …

The Transient Optical Sky Survey Data Pipeline, Elena Hadjiyska, Gary B. Hughes, Philip Lubin, Scott Taylor, Rory Hartong-Redden, Joshua Zierten

Statistics

The Transient Optical Sky Survey (TOSS) is an automated, ground-based telescope system dedicated to searching for optical transient events. Small telescope tubes are mounted on a tracking, semi-equatorial frame with a single polar axis. Each fixed-declination telescope records successive exposures which overlap in right ascension. Nightly observations produce time-series images of fixed fields within each declination band. We describe the TOSS data pipeline, including automated routines used for image calibration, object detection and identification, astrometry, and differential photometry. Time series of nightly observations are accumulated in a database for each declination band. Despite the modest cost of the mechanical system, …

New Results For Oscillatory Behavior Of Even-Order Half-Linear Delay Differential Equations, Chenghui Zhang, Ravi P. Agarwal, Martin Bohner, Tongxing Li

Mathematics and Statistics Faculty Research & Creative Works

Some new oscillation results are presented that improve those reported in [C. Zhang, T. Li, B. Sun, and E. Thandapani, On the oscillation of higher-order half-linear delay differential equations, Appl. Math. Lett. 24 (2011) 1618-1621]. © 2012 Elsevier Ltd. All rights reserved.

A Spectral Order For Infinite Dimensional Quantum Spaces, Joe Mashburn

Mathematics Faculty Publications

In this paper we extend the spectral order of Coecke and Martin to infinite-dimensional quantum states. Many properties present in the finite-dimensional case are preserved, but some of the most important are lost. The order is constructed and its properties analysed. Most of the useful measurements of information content are lost. Shannon entropy is defined on only a part of the model, and that part is not a closed subset of the model. The finite parts of the lattices used by Birkhoff and von Neumann as models for classical and quantum logic appear as subsets of the models for infinite …

Some Minor-Closed Classes Of Signed Graphs, Dan Slilaty, Xiangqian Zhou

Mathematics and Statistics Faculty Publications

We define four minor-closed classes of signed graphs in terms of embeddability in the annulus, projective plane, torus, and Klein bottle. We give the full list of 20 excluded minors for the smallest class and make a conjecture about the largest class.

3e: Energy-Efficient Elastic Scheduling For Independent Tasks In Heterogeneous Computing Systems, Xiaomin Zhu, Rong Ge, Jinguang Sun, Chuan He

Mathematics, Statistics and Computer Science Faculty Research and Publications

Reducing energy consumption is a major design constraint for modern heterogeneous computing systems to minimize electricity cost, improve system reliability and protect environment. Conventional energy-efficient scheduling strategies developed on these systems do not sufficiently exploit the system elasticity and adaptability for maximum energy savings, and do not simultaneously take account of user expected finish time. In this paper, we develop a novel scheduling strategy named energy-efficient elastic (3E) scheduling for aperiodic, independent and non-real-time tasks with user expected finish times on DVFS-enabled heterogeneous computing systems. The 3E strategy adjusts processors’ supply voltages and frequencies according to the system workload, and …

The Performance Of Mlem For Dynamic Imaging From Simulated Few-View, Multi-Pinhole Spect, Dan Ma, Paul Arthur Wolf, Anne V. Clough, Taly Gilat Schmidt

Mathematics, Statistics and Computer Science Faculty Research and Publications

Stationary small-animal SPECT systems are being developed for rapid dynamic imaging from limited angular views. This work quantified, through simulations, the performance of Maximum Likelihood Expectation Maximization (MLEM) for reconstructing a time-activity curve (TAC) with uptake duration of a few seconds from a stationary, three-camera multi-pinhole SPECT system. The study also quantified the benefits of a heuristic method of initializing the reconstruction with a prior image reconstructed from a conventional number of views, for example from data acquired during the late-study portion of the dynamic TAC. We refer to MLEM reconstruction initialized by a prior-image initial guess (IG) as MLEM …

“Seeing” The Elephant: Assessing The Impact Of Library-Composition Program Collaboration On First-Year Student Learning, Erin E. Rinto

Library Faculty Presentations

Though university libraries and composition programs have historically collaborative relationships, these partnerships can take a variety of formats, including single course period library sessions, teaching-the-teachers, and librarian-driven assignment models. A hybrid of these collaborative approaches was implemented Fall 2012 at UNLV in an effort to provide first-year composition students with a more systematic information literacy experience in the required ENG 102 course. A two-pronged assessment method was used to evaluate the impact of the collaboration for both first-year student learning as well as to implement programmatic change.

Accounting For Model Uncertainty In Linear Mixed-Effects Models, Adam Sima

Theses and Dissertations

Standard statistical decision-making tools, such as inference, confidence intervals and forecasting, are contingent on the assumption that the statistical model used in the analysis is the true model. In linear mixed-effect models, ignoring model uncertainty results in an underestimation of the residual variance, contributing to hypothesis tests that demonstrate larger than nominal Type-I errors and confidence intervals with smaller than nominal coverage probabilities. A novel utilization of the generalized degrees of freedom developed by Zhang et al. (2012) is used to adjust the estimate of the residual variance for model uncertainty. Additionally, the general global linear approximation is extended to …

U.S. Employment Outlook For 2013, Randall W. Eberts

Periodical Articles

No abstract provided.

Targeted Data Adaptive Estimation Of The Causal Dose Response Curve, Iván Díaz, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

Estimation of the causal dose-response curve is an old problem in statistics. In a non parametric model, if the treatment is continuous, the dose-response curve is not a pathwise differentiable parameter, and no root-n-consistent estimator is available. However, the risk of a candidate algorithm for estimation of the dose response curve is a pathwise differentiable parameter, whose consistent and efficient estimation is possible. In this work, we review the cross validated augmented inverse probability of treatment weighted estimator (CV A-IPTW) of the risk, and present a cross validated targeted minimum loss based estimator (CV-TMLE) counterpart. These estimators are proven consistent …

Can Changes In Angiogenic Biomarkers Between The First And Second Trimesters Of Pregnancy Predict Development Of Pre-Eclampsia In A Low-Risk Nulliparous Patient Population?, Leslie Myatt, Rebecca G. Clifton, J. M. Roberts, Catherine Y. Spong, Ronald J. Wapner, +10 Additional Authors

GW Biostatistics Center

OBJECTIVE:

To determine if change in maternal angiogenic biomarkers between the first and second trimesters predicts pre-eclampsia in low-risk nulliparous women.

DESIGN:

A nested case-control study of change in maternal plasma soluble Flt-1 (sFlt-1), soluble endoglin (sEng) and placenta growth factor (PlGF). We studied 158 pregnancies complicated by pre-eclampsia and 468 normotensive nonproteinuric controls.

SETTING:

A multicentre study in 16 academic medical centres in the USA.

POPULATION:

Low-risk nulliparous women.

METHODS:

Luminex assays for PlGF, sFlt-1 and sEng performed on maternal EDTA plasma collected at 9-12, 15-18 and 23-26 weeks of gestation. Rate of change of analyte between first and …

From Solute Transport To Chemical Weathering, Allen Hunt, Thomas E. Skinner

Physics Seminars

A theory for conservative solute transport, based on concepts from percolation theory, is applied directly to reactive solute transport. Chemical reactions are assumed to have reached equilibrium at the scale of an individual pore, but at larger length scales, equilibration is limited by solute transport velocities, which are not the same as fluid velocities! The results of this theory already predicted observed dispersivity values for conservative solute transport over ten orders of magnitude of length scale as well as the variation of solute arrival time distributions with medium saturation. We now show that the solute velocity predicts the time-dependence of …

Statistical Methods For Evaluating And Comparing Biomarkers For Patient Treatment Selection, Holly Janes, Marshall D. Brown, Margaret Pepe, Ying Huang

UW Biostatistics Working Paper Series

Despite the heightened interest in developing biomarkers predicting treatment response that are used to optimize patient treatment decisions, there has been relatively little development of statistical methodology to evaluate these markers. There is currently no unified statistical framework for marker evaluation. This paper proposes a suite of descriptive and inferential methods designed to evaluate individual markers and to compare candidate markers. An R software package has been developed which implements these methods. Their utility is illustrated in the breast cancer treatment context, where candidate markers are evaluated for their ability to identify a subset of women who do not benefit …

An Evaluation Of Inferential Procedures For Adaptive Clinical Trial Designs With Pre-Specified Rules For Modifying The Sample Size, Greg P. Levin, Sarah C. Emerson, Scott S. Emerson

UW Biostatistics Working Paper Series

Many papers have introduced adaptive clinical trial methods that allow modifications to the sample size based on interim estimates of treatment effect. There has been extensive commentary on type I error control and efficiency considerations, but little research on estimation after an adaptive hypothesis test. We evaluate the reliability and precision of different inferential procedures in the presence of an adaptive design with pre-specified rules for modifying the sampling plan. We extend group sequential orderings of the outcome space based on the stage at stopping, likelihood ratio test statistic, and sample mean to the adaptive setting in order to compute …

Risk Score Modeling Of Multiple Gene To Gene Interactions Using Aggregated-Multifactor Dimensionality Reduction, Hongying Dai, Richard J. Charnigo, Mara L. Becker, J. Steven Leeder, Alison A. Motsinger-Reif

Statistics Faculty Publications

BACKGROUND: Multifactor Dimensionality Reduction (MDR) has been widely applied to detect gene-gene (GxG) interactions associated with complex diseases. Existing MDR methods summarize disease risk by a dichotomous predisposing model (high-risk/low-risk) from one optimal GxG interaction, which does not take the accumulated effects from multiple GxG interactions into account.

RESULTS: We propose an Aggregated-Multifactor Dimensionality Reduction (A-MDR) method that exhaustively searches for and detects significant GxG interactions to generate an epistasis enriched gene network. An aggregated epistasis enriched risk score, which takes into account multiple GxG interactions simultaneously, replaces the dichotomous predisposing risk variable and provides higher resolution in the quantification …

A Neural Network Model To Translate Brain Developmental Events Across Mammalian Species, Radhakrishnan Nagarajan, Jeffrey N. Jonkman

Biostatistics Faculty Publications

Translating the timing of brain developmental events across mammalian species using suitable models has provided unprecedented insights into neural development and evolution. More importantly, these models can prove to be useful abstractions and predict unknown events across species from known empirical event timing data retrieved from published literature. Such predictions can be especially useful since the distribution of the event timing data is skewed with a majority of events documented only across a few selected species. The present study investigates the choice of single hidden layer feed-forward neural networks (FFNN) for predicting the unknown events from the empirical data. A …

A General Regression Framework For A Secondary Outcome In Case-Control Studies, Eric J. Tchetgen Tchetgen

Harvard University Biostatistics Working Paper Series

No abstract provided.

In Praise Of Simplicity Not Mathematistry! Ten Simple Powerful Ideas For The Statistical Scientist, Roderick J. Little

The University of Michigan Department of Biostatistics Working Paper Series

Ronald Fisher was by all accounts a first-rate mathematician, but he saw himself as a scientist, not a mathematician, and he railed against what George Box called (in his Fisher lecture) "mathematistry". Mathematics is the indispensable foundation for statistics, but our subject is constantly under assault by people who want to turn statistics into a branch of mathematics, making the subject as impenetrable to non-mathematicians as possible. Valuing simplicity, I describe ten simple and powerful ideas that have influenced my thinking about statistics, in my areas of research interest: missing data, causal inference, survey sampling, and statistical modeling in general. …

Catching A Viral Video, T Broxton, Yannet Interian, J Vaver, M Wattenhofer

Master of Science in Analytics (MSAN) Faculty Research

The sharing and re-sharing of videos on social sites, blogs e-mail, and other means has given rise to the phenomenon of viral videos - videos that become popular through internet sharing. In this paper we seek to better understand viral videos on YouTube by analyzing sharing and its relationship to video popularity using millions of YouTube videos. The socialness of a video is quantified by classifying the referrer sources for video views as social (e.g. an emailed link, Facebook referral) or non-social (e.g. a link from related videos). We find that viewership patterns of highly social videos are very different …

Modeling The Impact And Costs Of Semiannual Mass Drug Administration For Accelerated Elimination Of Lymphatic Filariasis, Wilma A. Stolk, Quirine A. Ten Bosch, Sake J. De Vlas, Peter U. Fischer, Gary J. Weil, Ann S. Goldman

Epidemiology Faculty Publications

The Global Program to Eliminate Lymphatic Filariasis (LF) has a target date of 2020. This program is progressing well in many countries. However, progress has been slow in some countries, and others have not yet started their mass drug administration (MDA) programs. Acceleration is needed. We studied how increasing MDA frequency from once to twice per year would affect program duration and costs by using computer simulation modeling and cost projections. We used the LYMFASIM simulation model to estimate how many annual or semiannual MDA rounds would be required to eliminate LF for Indian and West African scenarios with varied …