Simultaneously Testing for Location and Scale Parameters of Two Multivariate Distributions

In this article, we propose nonparametric tests for simultaneously testing equality of location and scale parameters of two multivariate distributions by using nonparametric combination theory. Our approach is to combine the data depth based location and scale tests using combining function to construct a new data depth based test for testing both location and scale parameters. Based on this approach, we have proposed several tests. Fisher's permutation principle is used to obtain p-values of the proposed tests. Performance of proposed tests has been evaluated in terms of empirical power for symmetric and skewed multivariate distributions and compared to the existing test based on data depth. The proposed tests are also applied to a real-life data set for illustrative purpose.

Tests for comparison of multiple endpoints with application to omics data

In biomedical research, multiple endpoints are commonly analyzed in “omics” fields like genomics, proteomics and metabolomics. Traditional methods designed for low-dimensional data either perform poorly or are not applicable when analyzing high-dimensional data whose dimension is generally similar to, or even much larger than, the number of subjects. The complex biochemical interplay between hundreds (or thousands) of endpoints is reflected by complex dependence relations. The aim of the paper is to propose tests that are very suitable for analyzing omics data because they do not require the normality assumption, are powerful also for small sample sizes, in the presence of complex dependence relations among endpoints, and when the number of endpoints is much larger than the number of subjects. Unbiasedness and consistency of the tests are proved and their size and power are assessed numerically. It is shown that the proposed approach based on the nonparametric combination of dependent interpoint distance tests is very effective. Applications to genomics and metabolomics are discussed.

Nonparametric combination tests for comparing two survival curves with informative and non-informative censoring

This paper looks at permutation methods used to deal with hypothesis testing within the survival analysis framework. In the literature, several attempts have been made to deal with the comparison of survival curves and, depending on the survival and hazard functions of two groups, they can be more or less efficient in detecting differences. Furthermore, in some situations, censoring can be informative in that it depends on treatment effect. Our proposal is based on the nonparametric combination approach and has proven to be very effective under different configurations of survival and hazard functions. It allows the practitioner to test jointly on primary and censoring events and, by using multiple testing methods, to assess the significance of the treatment effect separately on the survival and the censoring process.

Honor and War

Reputation has long been considered central to international relations, but unobservability, strategic selection, and endogeneity have handicapped quantitative research. A rare source of haphazard variation in the cultural origins of leaders-the fact that one-third of US presidents were raised in the American South, a well-studied example of a culture of honor-provides an opportunity to identify the effects of heightened concern for reputation for resolve. A formal theory that yields several testable predictions while accounting for unobserved selection into disputes is offered. The theory is illustrated through a comparison of presidents John F. Kennedy and Lyndon B. Johnson and systematically tested using matching, permutation inference, and the nonparametric combination of tests. Interstate conflicts under Southern presidents are shown to be twice as likely to involve uses of force, last on average twice as long, and are three times more likely to end in victory for the United States than disputes under non-Southern presidents. Other characteristics of Southern presidencies do not seem able to account for this pattern of results. Theresults provide evidence that concern for reputation is an important cause of interstate conflict behavior.

The knowledge of Italian wines on export markets

Purpose – The European Union (EU) has strongly rearranged the management of EU wine policy by introducing actions for promoting wine in third countries. The purpose of this paper is to evaluate factors affecting the knowledge of Italian wines in foreign consumers, i.e., to what extend wine promotion actions can improve the consumer’s awareness or the reputation of Italian wines. As a consequence, these activities may increase the wine consumption as well as wine exports in emerging markets. Design/methodology/approach – Data have been collected through survey questionnaires where information about wine tasting, sensory satisfaction and preferences about Italian wines have been collected. The sample survey collects preferences of wine market operators in both EU and third countries. The survey, carried out from 2009 to 2011, includes 3,579 interviews classified according to four promotion actions: press conference, wine tasting, tasting course, knowledge of Italian wines. Data have been analyzed through a nonparametric combination (NPC) of dependent permutation tests to evaluate differences between and within country groups and to assess the consumer perception about Italian wines through the Keller’s model. Findings – So far, Italian wine promotion activities, supported by EU wine policy, are fragmented among in many small and sometimes low effective actions. Research results may be helpful in designing more effective promotional strategies on third countries. In particular, promotional activities which should be focussed on consumer’s appreciation of Italian wines as a brand instead of promoting specific wines or wineries. Research limitations/implications – The NPC method is a nonparametric tool which does not measure the structure of consumer’s preferences, i.e, it does give any measure of relationships among consumer’s utility and factors affecting it as it happens when a modeling approach is applied. Practical implications – Targeted promotion and information actions strongly focussed internal and external wine attributes can increase the level of knowledge in foreign consumers. It can make more efficient the marketing activity oriented to the export market. Originality/value – The NPC method offers an innovative, flexible and well-tested approach for the analysis of multivariate hypothesis when we are dealing with complex problems in wine market.