On minimax designs when there are two candidate models

This work is motivated by the need to find experimental designs which are robust under different model assumptions. We measure robustness by calculating a measure of design efficiency with respect to a design optimality criterion and say that a design is robust if it is reasonably efficient under different model scenarios. We discuss two design criteria and an algorithm which can be used to obtain robust designs. The first criterion employs a Bayesian-type approach by putting a prior or weight on each candidate model and possibly priors on the corresponding model parameters. We define the first criterion as the expected value of the design efficiency over the priors. The second design criterion we study is the minimax design which minimizes the worst value of a design criterion over all candidate models. We establish conditions when these two criteria are equivalent when there are two candidate models. We apply our findings to the area of accelerated life testing and perform sensitivity analysis of designs with respect to priors and misspecification of planning values.     

Testing for mean and variance differences with samples from distributions that may be non-normal with unequal variances

The problem of comparing several samples to decide whether the means and/or variances are significantly different is considered. It is shown that with very non-normal distributions even a very robust test to compare the means has poor properties when the distributions have different variances, and therefore a new testing scheme is proposed. This starts by using an exact randomization test for any significant difference (in means or variances) between the samples. If a non-significant result is obtained then testing stops. Otherwise, an approximate randomization test for mean differences (but allowing for variance differences) is carried out, together with a bootstrap procedure to assess whether this test is reliable. A randomization version of Levene's test is also carried out for differences in variation between samples. The five possible conclusions are then that (i) there is no evidence of any differences, (ii) evidence for mean differences only, (iii) evidence for variance differences only, (iv) evidence for mean and variance differences, or (v) evidence for some indeterminate differences. A simulation experiment to assess the properties of the proposed scheme is described. From this it is concluded that the scheme is useful as a robust, conservative method for comparing samples in cases where they may be from very non-normal distributions.     

Optimal detection of Fechner-asymmetry

We consider a general class of skewed univariate densities introduced by Fechner [1897. Kollectivmasslehre. Engleman, Leipzig], and derive optimal testing procedures for the null hypothesis of symmetry within that class. Locally and asymptotically optimal (in the Le Cam sense) tests are obtained, both for the case of symmetry with respect to a specified location as for the case of symmetry with respect to some unspecified location. Signed-rank based versions of these tests are also provided. The efficiency properties of the proposed procedures are investigated by a derivation of their asymptotic relative efficiencies with respect to the corresponding Gaussian parametric tests based on the traditional Pearson–Fisher coefficient of skewness. Small-sample performances under several types of asymmetry are investigated via simulations.     

Crossover designs in the presence of carry-over effects from two factors

Experiments, used in the telecommunications industry and elsewhere, are considered that involve the simultaneous application of levels of two unrelated factors, treatments and stimuli, to each of several subjects in a succession of time periods. The existence is suspected of carry-over effects of treatments and stimuli, in the period immediately following the period of their application. Methods are given for the construction of separate sequences of treatments and of stimuli; these methods are based on the Latin squares of Williams and of Russell. In the resulting designs, the treatments and stimuli are either orthogonal or nearly orthogonal, and the coincidence of the direct and carry-over effects of each factor is either balanced or nearly balanced. The efficiencies of the designs are assessed by comparing the average variances of elementary contrasts in the levels of each factor with appropriate lower bounds.     

Financial Crisis and Sustainability of US Fiscal Deficit: Indicators or Tests?

Whether or not budgetary policies are sustainable and can be conducted without creating the potential for government bankruptcy is a central question for macroeconomic analysis. In this paper, we show that indicators and tests to assess government solvency should not be used alternatively. We lay out a simple and intuitive procedure to integrate simultaneously the results from the two approaches to fiscal sustainability. Indicators are forward looking, for they are based on published forecasts, thus reacting to a set of current and expected future conditions in fiscal-policy making. Tests, by contrast, are backward looking, for they are based on a sample of past data. In the event of conflicting results, indicators may signal the occurrence of a structural change in policy, which may reverse the predictions of tests. Whether the results from indicators or from tests should be given priority in the assessment of the sustainability of public debt will thus depend on the structural stability of the historical data generating process of the primary surplus. Only in the absence of a structural break in the stance of fiscal policy, the potential warning predictions of fiscal indicators should be interpreted as merely reflecting transitory factors to be eventually reversed. An application to U.S. post-World War II historical data, from 1948 to 2016, and forecasts, from 2017 to 2027, demonstrates the empirical relevance of the proposed comprehensive approach and helps add new insights to the evaluation of the U.S. fiscal position. In particular, our results suggest that the potentially unsustainable course of U.S. fiscal policy from 2008 onwards, advocated by the use of fiscal indicators, reflects systematic—not cyclical—factors. The main policy implication is that deficit increases in the U.S. from 2008 onwards cannot be regarded as a transitory phenomenon and hence do entail an urgent need for a structural change in the future stance of budgetary policy.     

《说文解字》禾部字的文化阐释

《说文解字》禾部字承载了中华民族丰富的历史文化信息。凭借对《说文解字》禾部字的系统梳理分析,再现了其所反映的复杂而多样的古代思想文化内涵。     

Appropriation et régulation des innovations biotechnologiques : pour une comparaison transatlantique

This article analyzes two biotechnological innovations — the tests of tracking the genetic risks of diseases and the transgenic organisms — and explores the controversies concerning the status of these new knowledges and the ways there are applied. It shows how these innovations were received in a different way in the United States and in France. The market regulation, which is strong in the USA is problematic in France. It is marginalized by the professional regulation in the case of the genetic tests. And in the other case it is limited by the control of the state, which constitutes some resources for the mobilization of the civil society against transgenic organisms. Finally the comparison consolidates the hypothesis of the emergence of a new regime of production of the knowledge, specified by the tension between a “market” regulation and a “consumerist-civic” regulation.     

中国国民收入与茶叶内销量的实证研究

通过Eviews3.1软件就1990年到2008年我国国民收入与茶叶内销售量关系进行分析,得出我国国民收入与茶叶内销量存在协整关系,同时运用格兰杰检验得出我国国民收入提高是我国茶叶内销量增加的成因,认为通过预测我国国民收入水平可推算出我国茶叶的内销量,为茶叶产销决策提供依据。     

Dynamics of Market Power and Concentration Profiles

This paper examines some of the economic and econometric issues that arise in attempting to measure the degree of concentration in an industry and its dynamic evolution. A general axiomatic basis is developed. We offer new measures of concentration over aggregated periods of time and provide a sound statistical basis for inferences. Concentration is one aspect of the problem of measuring “market power” within an industry. Modern economic analysis of antitrust issues does not focus only on the level of concentration, but still must examine the issue carefully. We contrast concentration at a point in time with a dynamic profile of change in the distribution of shares in a given market. Our methods are demonstrated with an application to the US steel industry.     

Publication Decisions Revisited: The Effect of the Outcome of Statistical Tests on the Decision to Publish and Vice Versa

This article presents evidence that published results of scientific investigations are not a representative sample of results of all scientific studies. Research studies from 11 major journals demonstrate the existence of biases that favor studies that observe effects that, on statistical evaluation, have a low probability of erroneously rejecting the so-called null hypothesis (H ₀). This practice makes the probability of erroneously rejecting H ₀ different for the reader than for the investigator. It introduces two biases in the interpretation of the scientific literature: one due to multiple repetition of studies with false hypothesis, and one due to failure to publish smaller and less significant outcomes of tests of a true hypotheses. These practices distort the results of literature surveys and of meta-analyses. These results also indicate that practice leading to publication bias have not changed over a period of 30 years.