3,382 research outputs found

    On A Simpler and Faster Derivation of Single Use Reliability Mean and Variance for Model-Based Statistical Testing

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    Markov chain usage-based statistical testing has proved sound and effective in providing audit trails of evidence in certifying software-intensive systems. The system end-toend reliability is derived analytically in closed form, following an arc-based Bayesian model. System reliability is represented by an important statistic called single use reliability, and defined as the probability of a randomly selected use being successful. This paper continues our earlier work on a simpler and faster derivation of the single use reliability mean, and proposes a new derivation of the single use reliability variance by applying a well-known theorem and eliminating the need to compute the second moments of arc failure probabilities. Our new results complete a new analysis that could be shown to be simpler, faster, and more direct while also rendering a more intuitive explanation. Our new theory is illustrated with three simple Markov chain usage models with manual derivations and experimental results

    Estimation and model selection in generalized additive partial linear models for correlated data with diverging number of covariates

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    We propose generalized additive partial linear models for complex data which allow one to capture nonlinear patterns of some covariates, in the presence of linear components. The proposed method improves estimation efficiency and increases statistical power for correlated data through incorporating the correlation information. A unique feature of the proposed method is its capability of handling model selection in cases where it is difficult to specify the likelihood function. We derive the quadratic inference function-based estimators for the linear coefficients and the nonparametric functions when the dimension of covariates diverges, and establish asymptotic normality for the linear coefficient estimators and the rates of convergence for the nonparametric functions estimators for both finite and high-dimensional cases. The proposed method and theoretical development are quite challenging since the numbers of linear covariates and nonlinear components both increase as the sample size increases. We also propose a doubly penalized procedure for variable selection which can simultaneously identify nonzero linear and nonparametric components, and which has an asymptotic oracle property. Extensive Monte Carlo studies have been conducted and show that the proposed procedure works effectively even with moderate sample sizes. A pharmacokinetics study on renal cancer data is illustrated using the proposed method.Comment: Published in at http://dx.doi.org/10.1214/13-AOS1194 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

    China's Foreign Aid Policy and Architecture

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    As China's engagement in low?income countries has deepened, particularly in Africa, so has criticism of China's development programmes and practices. New developments in Africa and the international aid architecture warrant a re?examination of China's foreign assistance and development architecture, and its capacity in managing this growing engagement. This article outlines the modes of Chinese foreign assistance, the institutional arrangements and the principles that guide it. It argues that, while China's foreign aid has been characterised by several strengths, including its practical orientation, its consistency of principles, and its focus on high?level exchanges, these same features may also be fault lines for both the future effectiveness of China's aid programmes, and its international reputation as a rising power in development. Evaluation and future reform of China's aid architecture is needed in order to enhance China's aid capacity and effectiveness

    Estimation and Testing for Varying Coefficients in Additive Models with Marginal Integration

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    We propose marginal integration estimation and testing methods for the coefficients of varying coefficient multivariate regression model. Asymptotic distribution theory is developed for the estimation method which enjoys the same rate of convergence as univariate function estimation. For the test statistic, asymptotic normal theory is established. These theoretical results are derived under the fairly general conditions of absolute regularity (beta-mixing). Application of the test procedure to the West German real GNP data reveals that a partially linear varying coefficient model is best parsimonious in fitting the data dynamics, a fact that is also confirmed with residual diagnostics.adaptive volatility estimation, generalized hyperbolic distribution, value at risk, risk management
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