Theses and Dissertations at Montana State University (MSU)
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Item Statistical methodology for biological signals in the presence of measurement uncertainty(Montana State University - Bozeman, College of Letters & Science, 2018) Barbour, Christopher Robert; Chairperson, Graduate Committee: Mark Greenwood; Bibiana Bielekova (co-chair); Mark Greenwood, Dominique Zosso and Bibiana Bielekova were co-authors of the article, 'Constructed composite response: a framework for constructing targeted latent variables' submitted to the journal 'Biometrika' which is contained within this dissertation.; Christopher Barbour, Mark Greenwood, Dominique Zosso and Bibiana Bielekova were co-authors of the article, 'Extending CCR methodology to high-dimensional data to develop a sensitive clinical endpoint for multiple sclerosis' submitted to the journal 'Computational and graphical statistics' which is contained within this dissertation.; Peter Kosa, Mika Komori, Makoto Tanigaw, Ruturaj Masvekar, Tianxia Wu, Kory Johnson, Panagiotis Douvaras, Valentina Fossati, Ronald Herbst, Yue Wang, Keith Tan, Mark Greenwood and Bibiana Bielekova were co-authors of the article, 'Molecular-based diagnosis of multiple sclerosis and its progressive stage' in the journal 'Annals of neurology' which is contained within this dissertation.In recent years, increasing amounts of complex biological data are being collected on patients in many branches of medical research. Many of these signals are being collected with a certain amount of imprecision in the attained measurements. Two such areas in multiple sclerosis (MS) research are clinical scale development and proteomics analysis. Scales are often constructed from multiple outcome measures to create a combined metric that is a better measure of the true trait of interest than any of the original components. When the interest is in creating a scale that is sensitive to changes over time, developing it using cross-sectional data may not tune the projection to detect changes over time optimally. The proposed methodology, coined the Constructed Composite Response (CCR), was developed to maximize detected longitudinal change. A simulation study, and analysis of a motivating dataset, demonstrated that the CCR methodology performs better at capturing longitudinal change than traditional techniques. Including sparsifying constraints, motivated by penalized regression models, improved the performance of the CCR in high- dimensional data. In proteomics data, undesirable sources of variation are often present. Examples include temporal fluctuation in control samples and technical variability from multiple assay runs. When developing a molecular classifier of MS, a novel variable screening procedure was implemented to eliminate proteins with high levels of these unwanted sources. A simulation study compared this with traditional screening approaches and findings are discussed. Future extensions and directions of research are also discussed.Item Event-triggered causality: a causality detection tool for big data(Montana State University - Bozeman, College of Engineering, 2018) Davis, Tyler Bruce; Chairperson, Graduate Committee: Ross K. SniderFinding causal relationships in time series data is a well-known problem and methods such as Granger causality or transfer entropy look for it in continuous data sources. However, when data contains discrete events and comes from multiple sources with varying data types, assumptions underlying these methods are often violated. We present a new method called Event Triggered Causality (ETC) that can determine causal relationships between observed events within time series data from very different sensors. The new causality metric takes a data mining approach where events in the data are first identified with data dependent event detectors. The events are then clustered according to their spectral fingerprints and assessed for causality using both similarity and predictability measures. Event similarity is measured using distance metrics while temporal predictability is measured using a temporal entropy metric. ETC is then extended to find successive causal links between events, called Directed Event Triggered Causality, which takes the form of a directed graph. We use these methods to analyze potential causal links in two different situations. The first is searching for causal links between marmoset vocal interactions and related movements. The second is between commands from a farmer, his sheep dog, and the movement of sheep. The construction of these metrics helps to expand the definition of event-based causality and provides a method to further understand complex systems such as social and behavioral interactions.Item Homogeneity measurements in parent-child webpage relationships(Montana State University - Bozeman, College of Engineering, 2002) Livingood, Bejamin