Browsing by Subject "Bayesian models"

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    Computational issues in using Bayesian hierarchical methods for the spatial modeling of fMRI data.
    (2010-08) Lee, Kuo-Jung
    One of the major objectives of fMRI (functional magnetic resonance imaging) studies is to determine which areas of the brain are activated in response to a stimulus or task. To make inferences about task-specific changes in underlying neuronal activity, various statistical models are used such as general linear models (GLMs). Frequentist methods assessing human brain activity using data from fMRI experiments rely on results from the theory of Gaussian random fields. Such methods have several limitations. The Bayesian paradigm provides an attractive framework for making inference using complex models and bypassing the multiple comparison problems. We propose a Bayesian model which not only takes into account the complex spatio-temporal relationships in the data while still being computationally feasible, but gives a framework for addressing other interesting questions related to how the human brain works. We study the properties of this approach and demonstrate its performance on simulated and real examples.
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    Data and model code for assessing dabbling duck age ratios and corresponding environmental correlates in the North American Prairies, 1969-2015
    (2018-05-16) Specht, Hannah M; Arnold, Todd W; spech030@umn.edu; Specht, Hannah M
    Fecundity estimates for demographic modeling are difficult to acquire at the regional spatial scales that correspond to climate shifts, land use impacts or habitat management programs, yet are important for evaluating such effects. While waterfowl managers have historically used harvest-based age ratios to assess fecundity at continental scales, widely available age ratios from late-summer banding data present an underutilized opportunity to examine a regional fecundity index with broad temporal replication. We used age ratios from banding data and hierarchical mixed-effect models to examine how fecundity of five North American dabbling duck species was affected by temporal variation in hydrological cycles, intra- and inter-specific density dependence and alternate prey availability, and whether those relationships were consistent across a broad geographic area. The data and code for these analysis are included here.