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排序方式: 共有3203条查询结果,搜索用时 318 毫秒
941.
J. Denis Sargan 《Econometric Reviews》2001,20(2):159-170
This paper defines the phenomenon of data mining in econometrics and discusses various outcomes of and solutions to data mining. Both classical and Bayesian approaches are considered, each with notable advantages and disadvantages, and with the choice of loss function affecting critical values. Illustrative examples include variable addition and exclusion in a standard linear regression model, the choice of lag structure in a dynamic single equation, and specification in a simultaneous equations model. 相似文献
942.
Marlene Müller 《Statistics and Computing》2001,11(4):299-309
A particular semiparametric model of interest is the generalized partial linear model (GPLM) which extends the generalized linear model (GLM) by a nonparametric component.The paper reviews different estimation procedures based on kernel methods as well as test procedures on the correct specification of this model (vs. a parametric generalized linear model). Simulations and an application to a data set on East–West German migration illustrate similarities and dissimilarities of the estimators and test statistics. 相似文献
943.
In this paper, we develop procedures to test hypotheses concerning transition probability matrices arising from certain nonhomogeneous
Markov processes. It is assumed that the data consist of sample paths, some of which are observed until a certain terminal
state, and the other paths are censored. Problems of this type arise in the context of multi-state models relevant to Health
Related Quality of Life (HRQoL) and Competing Risks. The test statistic is based on the estimator for the associated intensity
matrix. We show that the asymptotic null distribution of the proposed statistic is Gaussian, and demonstrate how the procedure
can be adopted for HRQoL studies and competing risks model using real data sets. Finally, we establish that the test statistic
for the HRQoL has greatest local asymptotic power against a sequence of proportional hazards alternatives converging to the
null hypothesis. 相似文献
944.
Helmut Rieder Matthias Kohl Peter Ruckdeschel 《Statistical Methods and Applications》2008,17(1):13-40
Robust Statistics considers the quality of statistical decisions in the presence of deviations from the ideal model, where
deviations are modelled by neighborhoods of a certain size about the ideal model. We introduce a new concept of optimality
(radius-minimaxity) if this size or radius is not precisely known: for this notion, we determine the increase of the maximum
risk over the minimax risk in the case that the optimally robust estimator for the false neighborhood radius is used. The
maximum increase of the relative risk is minimized in the case that the radius is known only to belong to some interval [r
l
,r
u
]. We pursue this minmax approach for a number of ideal models and a variety of neighborhoods. Also, the effect of increasing
parameter dimension is studied for these models. The minimax increase of relative risk in case the radius is completely unknown,
compared with that of the most robust procedure, is 18.1% versus 57.1% and 50.5% versus 172.1% for one-dimensional location
and scale, respectively, and less than 1/3 in other typical contamination models. In most models considered so far, the radius
needs to be specified only up to a factor , in order to keep the increase of relative risk below 12.5%, provided that the radius–minimax robust estimator is employed.
The least favorable radii leading to the radius–minimax estimators turn out small: 5–6% contamination, at sample size 100.
相似文献
945.
Regarding the effect of product variety on purchase probability, there exist findings which demonstrate a positive effect
of variety for small assortments and a negative effect of variety for large assortments. Despite these results, little evidence
exists about the causal mechanism of this effect. We conduct a field study among German consumer electronics customers to
investigate the previously proposed constructs of anticipated product utility, anticipated regret and evaluation costs. The
results suggest that anticipated regret and evaluation costs play a powerful role in explaining the negative link between
variety and purchase probability for high variety assortments. Anticipated product utility on the other hand serves to explain
part of the positive causality for low variety assortments. The results obtained give rise to recommendations for the planning
of assortments.
相似文献
Andreas HerrmannEmail: |
946.
This paper presents a method for constructing confidence intervals for the median of a finite population under unequal probability sampling. The model-assisted approach makes use of the L1-norm to motivate the estimating function which is then used to develop a unified approach to inference which includes not only confidence intervals but hypothesis tests and point estimates. The approach relies on large sample theory to construct the confidence intervals. In cases when second-order inclusion probabilities are not available or easy to compute, the Hartley–Rao variance approximation is employed. Simulations show that the confidence intervals achieve the appropriate confidence level, whether or not the Hartley–Rao variance is employed. 相似文献
947.
法律秩序的功能限度与社会拒绝之补救 总被引:1,自引:0,他引:1
杨力 《河北大学学报(哲学社会科学版)》2005,30(1):35-37
通过对法律秩序功能实现中的外在强制与内在制约、资源稀缺与秩序公正以及规则适用与自由裁量的探讨,一方面,展现一种由于法律秩序的内部冲突和关系紧张引发的社会拒绝;另方面,更本质地意义在于两个极点间中寻求一种必要张力,以降低法律秩序功能实现所必需付出的代价,实现社会的和谐状态 相似文献
948.
John C. Chao Norman R. Swanson 《Econometrica : journal of the Econometric Society》2005,73(5):1673-1692
This paper analyzes the conditions under which consistent estimation can be achieved in instrumental variables (IV) regression when the available instruments are weak and the number of instruments, Kn, goes to infinity with the sample size. We show that consistent estimation depends importantly on the strength of the instruments as measured by rn, the rate of growth of the so‐called concentration parameter, and also on Kn. In particular, when Kn→∞, the concentration parameter can grow, even if each individual instrument is only weakly correlated with the endogenous explanatory variables, and consistency of certain estimators can be established under weaker conditions than have previously been assumed in the literature. Hence, the use of many weak instruments may actually improve the performance of certain point estimators. More specifically, we find that the limited information maximum likelihood (LIML) estimator and the bias‐corrected two‐stage least squares (B2SLS) estimator are consistent when , while the two‐stage least squares (2SLS) estimator is consistent only if Kn/rn→0 as n→∞. These consistency results suggest that LIML and B2SLS are more robust to instrument weakness than 2SLS. 相似文献
949.
Etebong P. Clement 《统计学通讯:理论与方法》2018,47(12):2835-2847
This study proposes a more efficient calibration estimator for estimating population mean in stratified double sampling using new calibration weights. The variance of the proposed calibration estimator has been derived under large sample approximation. Calibration asymptotic optimum estimator and its approximate variance estimator are derived for the proposed calibration estimator and existing calibration estimators in stratified double sampling. Analytical results showed that the proposed calibration estimator is more efficient than existing members of its class in stratified double sampling. Analysis and evaluation are presented. 相似文献
950.
In this paper, we introduce two kinds of new restricted estimators called restricted modified Liu estimator and restricted modified ridge estimator based on prior information for the vector of parameters in a linear regression model with linear restrictions. Furthermore, the performance of the proposed estimators in mean squares error matrix sense is derived and compared. Finally, a numerical example and a Monte Carlo simulation are given to illustrate some of the theoretical results. 相似文献