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941.
探讨了一种基于投影方式的阵列天线方向图综合法,并以17个单元的线阵为例,在FFT的抽样点为128个时,在计算机上完成了笔状形和CSC2波形综合图的模拟。模拟结果证明用最小均方误差准则或极小化最大误差准则获得所需的方向图和综合方向图最小的误差是有效的。 相似文献
942.
Suling Kang Rashid Abbasi Huiling Wang Xiaofeng Wang Yuanyan Tang 《统计学通讯:理论与方法》2018,47(21):5369-5377
Under mild conditions, we study the asymptotic behaviour of the uniformly strong consistency of the frequency polygon investigated by Scott under φ ?mixing samples. The results obtained weaken the relevant conditions used by Carbon et al. [6]. 相似文献
943.
In this paper, we study a k-step-stress accelerated life test under Type-I censoring. The lifetime of the items follows the multivariate exponential distribution and a cumulative exposure model is considered. We derive the maximum likelihood estimators of the model parameters and establish the asymptotic properties of them. The problem of choosing the optimal time is addressed by using V-optimality as well as D-optimality criteria. Finally, some numerical studies are discussed to illustrate the proposed procedures. 相似文献
944.
Mingtian Tang 《统计学通讯:理论与方法》2014,43(14):3047-3056
An integer-valued autoregressive model with random time delay under random environment is presented. The geometric ergodicity of the iterative sequence determined by this new model is discussed. Moreover, sufficient conditions for stationarity and β-mixing property with exponential decay for the INAR model with random time delay under random environment are developed. 相似文献
945.
It is quite common that raters may need to classify a sample of subjects on a categorical scale. Perfect agreement can rarely be observed partly because of different perceptions about the meanings of the category labels between raters and partly because of factors such as intrarater variability. Usually, category indistinguishability occurs between adjacent categories. In this article, we propose a simple log-linear model combining ordinal scale information and category distinguishability between ordinal categories for modelling agreement between two raters. For the proposed model, no score assignment is required to the ordinal categories. An algorithm and statistical properties will be provided. 相似文献
946.
Although multiple indices were introduced in the area of agreement measurements, the only documented index for linear relational agreement, which is for interval scale data, is the Pearson product-moment correlation coefficient. Despite its meaningfulness, the Pearson product-moment correlation coefficient does not convey the practical information such as what proportion of observations is within a certain boundary of the target value. To address this need, based on the inverse regression, we proposed the adjusted mean squared deviation (AMSD), adjusted coverage probability (ACP), and adjusted total deviation index (ATDI) for the measurement of the relational agreement. They can serve as reasonable and practically meaningful measurements for relational agreement. Real life data are considered to illustrate the performance of the methods. 相似文献
947.
Recently generalized exponential distribution has been discussed by many authors. In this article, we study the optimal constant-stress accelerated life tests with complete sample for the generalized exponential distribution. The problem of choosing the optimal proportions of test units allocated to each stress level is addressed by using V-optimality as well as D-optimality criteria. Some interesting conclusions are obtained. Finally, real data example and numerical examples have been analyzed to illustrate the proposed procedures. 相似文献
948.
In this article, Bayesian approach is applied to estimate the parameters of Log-logistic distribution under reference prior and Jeffreys’ prior. The reference prior is derived and it is found that the reference prior is also a second-order matching priors as for the case of any parameter of interest. The Bayesian estimators cannot be obtained in explicit forms. Metropolis within Gibbs sampling algorithm is used to obtain the Bayesian estimators. The Bayesian estimates are compared with the maximum likelihood estimates via simulation study. A real dataset is considered for illustrative purposes. 相似文献
949.
Large, family-based imaging studies can provide a better understanding of the interactions of environmental and genetic influences on brain structure and function. The interpretation of imaging data from large family studies, however, has been hindered by the paucity of well-developed statistical tools for that permit the analysis of complex imaging data together with behavioral and clinical data. In this paper, we propose to use two methods for these analyses. First, a variance components model along with score statistics is used to test linear hypotheses of unknown parameters, such as the associations of brain measures (e.g., cortical and subcortical surfaces) with their potential genetic determinants. Second, we develop a test procedure based on a resampling method to assess simultaneously the statistical significance of linear hypotheses across the entire brain. The value of these methods lies in their computational simplicity and in their applicability to a wide range of imaging data. Simulation studies show that our test procedure can accurately control the family-wise error rate. We apply our methods to the detection of statistical significance of gender-by-age interactions and of the effects of genetic variation on the thickness of the cerebral cortex in a family study of major depressive disorder. 相似文献
950.
Treatment regimes are algorithms for assigning treatments to patients with complex diseases, where treatment consists of more than one episode of therapy, potentially with different dosages of the same agent or different agents. Sequentially randomized clinical trials are usually designed to evaluate and compare the effect of different treatment regimes. In such designs, eligible patients are first randomly assigned to receive one of the initial treatments. Patients meeting some criteria (e.g. no progressive disease) are then randomized to receive one of the maintenance treatments. Usually, the procedure continues until all treatment options are exhausted. Such multistage treatment assignment results in treatment regimes consisting of initial treatments, intermediate responses and second-stage treatments. However, methods for efficient analysis of sequentially randomized trials have only been developed very recently. As a result, earlier clinical trials reported results based only on the comparison of stage-specific treatments. In this article, we propose a model that applies to comparisons of any combination of any number of treatment regimes regardless of the number of stages of treatment adjusted for auxiliary variables. Contrasts of treatment regimes are tested using the Wald chi-square method. Both the model and Wald chi-square tests of contrasts are illustrated through a simulation study and an application to a high-risk neuroblastoma study to complement the earlier results reported on this study. 相似文献