1,721,090 research outputs found
Tests for comparison of multiple endpoints with application to omics data
No full textIn 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
Perceived Justifiability Towards Morally Debatable Behaviors Across Europe
No full textScientific interest in studying justifiability towards morally debatable behaviors across nations is considerable, but the statistical assessment of the issue has not been very rigorous so far. In fact, many authors measure the related constructs computing composite indicators of justifiability as unweighed averages of perceived justifiability towards morally debatable behaviors. Other than not allowing for different weights, another drawback is that even if the items have different variability, no transformation like the z score is typically applied before computing the average. Another major shortcoming of the available justifiability indexes is the lack of robustness analysis of the results, making their message weak. The aim of this paper is to design very general composite indicators of justifiability towards dishonest-illegal and personal-sexual behaviors without the shortcomings of the other indicators. The indexes are computed for a data set from the European Values Study covering 47 countries and regions. The results show that Sweden, Netherlands and Finland are the most permissive countries towards personal-sexual behaviors followed by other Western and Scandinavian countries, whereas the strictest countries are Kosovo and Turkey. The most permissive countries towards dishonest-illegal behaviors are all ex-communist countries with Belarus and Slovak Republic being the most permissive countries whereas the strictest ones are Northern Cyprus and Turkey
A combined bootstrap test for the two-sample location problem
No full textThe comparison of two samples is a problem very frequently encountered in practice. There is active interest in researching for tests that are powerful also when the data are not compatible with the assumptions of normality and equal variances–as it is common in many fields–while controlling their type-one error rate. The Yuen test is a familiar method based on trimmed means. There is no agreement in the literature about the preferable rate of trimming. This paper has two aims: to study the power of many Yuen tests with different trimming rates and propose a bootstrap test based on the combination of Yuen tests with different trimming rates. It is shown that the various Yuen tests have very different power for different distributions because the best rate of trimming depends on distribution tailweight. Conversely, the combined test is powerful irrespective to the underlying distribution
An index of teaching performance based on students' feedback
No full textEvaluation of teaching performance of faculty members, on the basis of students' feedback, is routinely performed by almost all tertiary education institutions. Objective assessment of faculty members requires a comprehensive index of teaching performance. A composite indicator is proposed to assess teaching performance of faculty members. It is based on the combination of several items evaluated by students such as punctuality, communication ability and subject coverage. Robustness of the indicator is assessed applying uncertainty analysis. An application to a data set from an Indian institution is presented. It is shown that the proposed index can be used to rank faculty members from the least to the worst performer according to students' feedback
A Bi-Aspect Nonparametric Test for the Multi-Sample Location Problem
No full textA bi-aspect nonparametric test for testing hypotheses of location shifts of two populations was proposed in literature. The test is based on the nonparametric combination of dependent tests theory and is obtained by combining the traditional permutation test for the two-sample location problem with a test that takes into account whether a sample observation is or is not greater than the pooled sample median. A natural multi-sample extension of the test is proposed. The extension is shown by simulation to behave very similarly to the bi-aspect test for the two-sample problem. In fact, it is shown that the proposed test is remarkably more powerful than the traditional permutation test for the multi-sample location problem under heavy-tailed distributions like the Cauchy, the half-Cauchy, the 10% and the 30% outlier distributions. When sampling from the double-exponential and the exponential distributions, the proposed test appears to be better on the whole than the traditional permutation test. Under the considered t2 distributions, the bi-aspect test is practically as powerful as the traditional permutation test. Whereas under normal, uniform and bimodal distributions it is slightly less powerful. Moreover, the proposed test maintained the type-one error rate close to the nominal significance level and was generally slightly conservative
Multivariate bi-aspect testing for the two-sample location problem
No full textThe multivariate extension of the bi-aspect nonparametric testing procedure for the two-sample location problem presented in Marozzi (2004) is discussed. Two solutions are presented: the former is focused on each variable, the latter is focused on each of the two aspects involved in the bi-aspect (the categorical and the numerical one). Formal proofs of exactness, unbiasedness, and consistency of the multivariate tests are given. Such properties hold even when population first and second moments do not exist
Nonparametric Phase-II control charts for monitoring high-dimensional processes with unknown parameters
No full textMonitoring multivariate and high-dimensional data streams is often an essential requirement for quality management in manufacturing and service sectors in the Industry 4.0 era. Identifying a suitable distribution for a multivariate data set, especially when the number of variables is much larger than the sample size, is often challenging. Consequently, in a high-dimensional set-up, that is, when the number of variables under investigation exceeds sample size, parametric methods are generally not reliable in practice. There are various nonparametric schemes based on data depth for multivariate process monitoring, which are applicable only when the sample size is reasonably larger than the number of variables in the process but not in a high-dimensional set-up. We discuss that most of these charts are not robust when the true process parameters are unknown. There are, however, some nonparametric schemes for a high-dimensional process, when true process parameters are known. Nevertheless, when process parameters are unknown, a highly robust nonparametric scheme for monitoring high-dimensional processes is not yet available. In this paper, we propose some Shewhart-type nonparametric monitoring schemes based on specific distance metrics for surveillance of multivariate as well as high-dimensional processes. Our proposed charts are easy to implement, interpret and also advantageous in simultaneous monitoring of multiple aspects. We discuss the design and implementation issues in details. We carry out a performance study using Monte Carlo simulations and illustrate the proposed methods using a dataset related to industrial production
A Global Rank of the Delphi survey items on the Futures Scenarios of the Familiy
No full textThis paper describes some of the results of the research conducted by the Delphi method on the family tomorrow. Some hypotheses of future scenarios useful to understand today and to equip themselves for tomorrow are evaluated by a selected group of experts. From the focus group material, 41 items were identified, divided into 7 sections corresponding to different thematic areas concerning the family. (Parents, spouses, extended family, children, housing, family models, politics and services, communication, solidarity).
The research was carried out in four successive surveys, the first through a face-to-face interview to 32 experts selected according to criteria of expertise on the theme of the family. The subsequent ones using a CAWI method (Computer Assisted Web Based Interview) based on the online self-compilation of a computerized questionnaire, for which the LimeSurvey software was used (www.limesurvey.org). Respondents were asked to provide two assessments. The first "Evolution", and "Relevance" assigning a value between 0 and 100. In order to evaluate the relative importance of the various items, the Global Rank approach based on compound indicators was used
A Method to Address the Effectiveness of the SIC Code for Selecting Comparable Firms
Full text linkTo find peer firms is very important in several situations, for example in equity valuation for publicly traded firms, as well as for not publicly traded ones. Very often the pay of a chief executive officer (CEO) is set at the basis of a peer compensation group. Financial policies are often driven by a response to peers. It is a very common approach to use industry membership given by the SEC (United States Security and Exchange Commission) SIC (Standard Industrial Classification) code to form peer groups. In the paper the effectiveness of the SIC code for selecting comparable firms is evaluated through nonparametric testing for difference in firm financial ratios
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