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101.
We propose an alternative solution to the discriminant problem, one that requires little more than a minimum familiarity with linear programming. The approach shows promise for eliminating the complexities of conventional statistical approaches without sacrificing the essential power of existing methods. 相似文献
102.
Implications of a probabilistic “random walk” model of incremental sales response to advertising are developed for various timing patterns of advertising expenditures. Maximum likelihood procedures for assessing advertising effectiveness and for estimating a decay (forgetting) rate are developed and applied to artificial data of known configuration and are used to assess the impact over time of a brochure program on mail-order sales. Results are also compared to those from alternative models involving various lag patterns in advertising effects. 相似文献
103.
The two-group discriminant problem has applications in many areas, for example, differentiating between good credit risks and poor ones, between promising new firms and those likely to fail, or between patients with strong prospects for recovery and those highly at risk. To expand our tools for dealing with such problems, we propose a class of nonpara-metric discriminant procedures based on linear programming (LP). Although these procedures have attracted considerable attention recently, only a limited number of computational studies have examined the relative merits of alternative formulations. In this paper we provide a detailed study of three contrasting formulations for the two-group problem. The experimental design provides a variety of test conditions involving both normal and nonnormal populations. Our results establish the LP model which seeks to minimize the sum of deviations beyond the two-group boundary as a promising alternative to more conventional linear discriminant techniques. 相似文献
104.
在中印共同崛起的大背景下,探究印度对中国崛起的认知尤为必要。通过皮尤"全球态度调查"项目的数据可见印度对中国崛起的认知呈现"负面"态势。究其原因,在个人层面,印度公众对中国的无知与冷漠以及某些媒体记者对中国的歪曲报道直接造成这一结果;在国家层面,中印之间在边界争端、西藏问题、中印巴和中美印这四个关键议题上存在分歧,而这些敏感的议题又通过媒体的肆意渲染而影响印度公众对中国崛起的认知;印度公众对中国崛起的认知源于中印之间存在的"安全困境"。 相似文献
105.
Junyi Chen Shahriar Kibriya David Bessler Edwin Price 《Journal of Policy Modeling》2018,40(4):663-684
Though recent literature uncovers linkages between commodity prices and conflict, the causal direction of the relationship remains ambiguous. We attempt to contribute to this strand of research by studying the dynamic relationship of commodity prices and the onsets of conflict events in Sudan. Using monthly data ranging from January 2001 through December 2012, we identify a structural breakpoint in the multivariate time series model of prices of the three staple foods (sorghum, millet, and wheat) and conflict measure (number of conflict events) in September of 2011. Applying structural vector autoregression (SVAR) and linear non-Gaussian acyclic model (LiNGAM), we find that wheat price fluctuation is a root cause of conflict events in Sudan. We recommend several policy and programmatic suggestions structured toward production, subsidy, price regulation and support for rural farmers and consumers to stabilize commodity prices. 相似文献
106.
This paper studies the graphs for which the linear relaxation of the 2-connected spanning subgraph polyhedron has integer
or half-integer extreme points. These graphs are called quasi-integer. For these graphs, the linear relaxation of the k-edge connected spanning subgraph polyhedron is integer for all k=4r, r≥1. The class of quasi-integer graphs is closed under minors and contains for instance the class of series-parallel graphs.
We discuss some structural properties of graphs which are minimally non quasi-integer graphs, then we examine some basic operations
which preserve the quasi-integer property. Using this, we show that the subdivisions of wheels are quasi-integer. 相似文献
107.
Wavelet analysis is a new mathematical method developed as a unified field of science over the last decade or so. As a spatially adaptive analytic tool, wavelets are useful for capturing serial correlation where the spectrum has peaks or kinks, as can arise from persistent dependence, seasonality, and other kinds of periodicity. This paper proposes a new class of generally applicable wavelet‐based tests for serial correlation of unknown form in the estimated residuals of a panel regression model, where error components can be one‐way or two‐way, individual and time effects can be fixed or random, and regressors may contain lagged dependent variables or deterministic/stochastic trending variables. Our tests are applicable to unbalanced heterogenous panel data. They have a convenient null limit N(0,1) distribution. No formulation of an alternative model is required, and our tests are consistent against serial correlation of unknown form even in the presence of substantial inhomogeneity in serial correlation across individuals. This is in contrast to existing serial correlation tests for panel models, which ignore inhomogeneity in serial correlation across individuals by assuming a common alternative, and thus have no power against the alternatives where the average of serial correlations among individuals is close to zero. We propose and justify a data‐driven method to choose the smoothing parameter—the finest scale in wavelet spectral estimation, making the tests completely operational in practice. The data‐driven finest scale automatically converges to zero under the null hypothesis of no serial correlation and diverges to infinity as the sample size increases under the alternative, ensuring the consistency of our tests. Simulation shows that our tests perform well in small and finite samples relative to some existing tests. 相似文献
108.
Alexei Onatski 《Econometrica : journal of the Econometric Society》2009,77(5):1447-1479
In this paper we study high‐dimensional time series that have the generalized dynamic factor structure. We develop a test of the null of k0 factors against the alternative that the number of factors is larger than k0 but no larger than k1>k0. Our test statistic equals maxk0<k k1(γk−γk+1)(γk+1−γk+2), where γi is the ith largest eigenvalue of the smoothed periodogram estimate of the spectral density matrix of data at a prespecified frequency. We describe the asymptotic distribution of the statistic, as the dimensionality and the number of observations rise, as a function of the Tracy–Widom distribution and tabulate the critical values of the test. As an application, we test different hypotheses about the number of dynamic factors in macroeconomic time series and about the number of dynamic factors driving excess stock returns. 相似文献
109.
《Risk analysis》2018,38(1):194-209
This article presents the findings from a numerical simulation study that was conducted to evaluate the performance of alternative statistical analysis methods for background screening assessments when data sets are generated with incremental sampling methods (ISMs). A wide range of background and site conditions are represented in order to test different ISM sampling designs. Both hypothesis tests and upper tolerance limit (UTL) screening methods were implemented following U.S. Environmental Protection Agency (USEPA) guidance for specifying error rates. The simulations show that hypothesis testing using two‐sample t ‐tests can meet standard performance criteria under a wide range of conditions, even with relatively small sample sizes. Key factors that affect the performance include unequal population variances and small absolute differences in population means. UTL methods are generally not recommended due to conceptual limitations in the technique when applied to ISM data sets from single decision units and due to insufficient power given standard statistical sample sizes from ISM. 相似文献
110.
Jianer Chen Xiuzhen Huang Iyad A. Kanj Ge Xia 《Journal of Combinatorial Optimization》2006,11(2):231-247
The notion of linear fpt-reductions has been recently introduced to derive strong computational lower bounds for well-known
NP-hard problems. In this paper, we formally investigate the notion of W[t]-hardness under the linear fpt-reduction, and study the structural properties of the corresponding complexity classes. Additional
complexity lower bounds on important computational problems are established. Some observations on structural properties of
the standard parameterized hierarchy, the W -hierarchy, are also presented.
In this paper, we always assume that complexity functions are “nice” with both domain and range being non-negative integers
and the values of the functions and their inverses can be easily computed. 相似文献