42,017 research outputs found

    Getting Started with Particle Metropolis-Hastings for Inference in Nonlinear Dynamical Models

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    This tutorial provides a gentle introduction to the particle Metropolis-Hastings (PMH) algorithm for parameter inference in nonlinear state-space models together with a software implementation in the statistical programming language R. We employ a step-by-step approach to develop an implementation of the PMH algorithm (and the particle filter within) together with the reader. This final implementation is also available as the package pmhtutorial in the CRAN repository. Throughout the tutorial, we provide some intuition as to how the algorithm operates and discuss some solutions to problems that might occur in practice. To illustrate the use of PMH, we consider parameter inference in a linear Gaussian state-space model with synthetic data and a nonlinear stochastic volatility model with real-world data.Comment: 41 pages, 7 figures. In press for Journal of Statistical Software. Source code for R, Python and MATLAB available at: https://github.com/compops/pmh-tutoria

    Habitat Benefit Assessment and Decisionmaking: A Report to the National Marine Fisheries Service

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    Habitats and the services they provide are part of our nation’s portfolio of natural capital assets. As for many components of this portfolio, it is difficult to assess the value of their services, and this complicates regulators’ investment decisions, especially when the alternative use is measurable. The principal objective of this report is to suggest possible strategies for the National Marine Fisheries Service (NMFS) as it applies economic analyses and arguments in support of the agency’s trustee responsibilities. Many approaches are possible, and as we discuss, the “right” strategy will depend on the questions asked, the resources available, and the agency’s role in the consultation process. We discuss in detail bioeconomic modeling and ecosystem indicator approaches to habitat value assessment. Although the approaches are discussed independently, multiple tools could be used simultaneously across different regions or within the same region on different aspects of one consultation.Bioeconomic, ecological indicators, ecosystem services

    A Systematic Mapping of Factors Affecting Accuracy of Software Development Effort Estimation

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    Software projects often do not meet their scheduling and budgeting targets. Inaccurate estimates are often responsible for this mismatch. This study investigates extant research on factors that affect accuracy of software development effort estimation. The purpose is to synthesize existing knowledge, propose directions for future research, and improve estimation accuracy in practice. A systematic mapping study (a comprehensive review of existing research) is conducted to identify such factors and their impact on estimation accuracy. Thirty-two factors assigned to four categories (estimation process, estimator’s characteristics, project to be estimated, and external context) are identified in a variety of research studies. Although the significant impact of several factors has been shown, results are limited by the lack of insight into the extent of these impacts. Our results imply a shift in research focus and design to gather more in-depth insights. Moreover, our results emphasize the need to argue for specific design decisions to enable a better understanding of possible influences of the study design on the credibility of the results. For software developers, our results provide a useful map to check the assumptions that undergird their estimates, to build comprehensive experience databases, and to adequately staff design projects

    Scaling the Digital Divide: Home Computer Technology and Student Achievement

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    Assesses the effect of access to home computers and broadband Internet on students' math and reading test scores and its potential to close the achievement gap for the disadvantaged. Considers the role of parental monitoring

    The Failed Promise of User Fees: Empirical Evidence from the United States Patent and Trademark Office

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    In an attempt to shed light on the impact of user-fee financing structures on the behavior of administrative agencies, we explore the relationship between the funding structure of the Patent and Trademark Office (PTO) and its examination practices. We suggest that the PTO’s reliance on prior grantees to subsidize current applicants exposes the Agency to a risk that its obligatory costs will surpass incoming fee collections. When such risks materialize, we hypothesize, and thereafter document, that the PTO will restore financial balance by extending preferential examination treatment—i.e., higher granting propensities and/or shorter wait times—to some technologies over others

    The Failed Promise of User Fees: Empirical Evidence from the United States Patent and Trademark Office

    Get PDF
    In an attempt to shed light on the impact of user-fee financing structures on the behavior of administrative agencies, we explore the relationship between the funding structure of the Patent and Trademark Office (PTO) and its examination practices. We suggest that the PTO’s reliance on prior grantees to subsidize current applicants exposes the Agency to a risk that its obligatory costs will surpass incoming fee collections. When such risks materialize, we hypothesize, and thereafter document, that the PTO will restore financial balance by extending preferential examination treatment—i.e., higher granting propensities and/or shorter wait times—to some technologies over others
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