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Dverview and Main Advances in Permutation Tests for Linear Regression Models

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Journal of Mathematics and System Science 2015年第2期5卷 53-59页

作者： Massimiliano Giacalone angela alibrandi School of Economics Management and Statistics Bologna University Piazza Scaravilli 2 Bologna Italy. Department of Economical Business and Environmental Sciences and Quantitative Methods Messina University Via dei Verdi 75Messina ltaly.

When the population, from which the samples are extracted, is not normally distributed, or if the sample size is particularly reduced, become preferable the use of not parametric statistic test. An alternative to the normal model is the permutation or randomization model. The permutation model is nonparametric because no formal assumptions are made about the population parameters of the reference distribution, i.e., the distribution to which an obtained result is compared to determine its probability when the null hypothesis is true. Typically the reference distribution is a sampling distribution for parametric tests and a permutation distribution for many nonparametric tests. Within the regression models, it is possible to use the permutation tests, considering their ownerships of optimality, especially in the multivariate context and the normal distribution of the response variables is not guaranteed. In the literature there are numerous permutation tests applicable to the estimation of the regression models. The purpose of this study is to examine different kinds of permutation tests applied to linear models, focused our attention on the specific test statistic on which they are based. In this paper we focused our attention on permutation test of the independent variables, proposed by Oja, and other methods to effect the inference in non parametric way, in a regression model. Moreover, we show the recent advances in this context and try to compare them.

关键词： Permutation Tests Linear Regression Models Non Parametric Approach.

COVID-19 Pandemic Waves in Italy: An Epidemiological Overview about Infections, Swabs and Death Rates

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Open Journal of Epidemiology 2022年第3期12卷 285-299页

作者： Agata Zirilli Francesco Limonti angela alibrandi Department of Economics University of Messina Messina Italy Valle d’Itria Hospital Local Health Authority Taranto Italy

Introduction: On March 11, 2020, the World Health Organization (WHO) declared that the entire World was overrun by a pandemic. Science has managed, in a short time, to characterize a new disease, sequence a new viral genome, develop diagnostics, produce treatment protocols and establish the efficacy of drugs and vaccines in randomized controlled trials. In this paper we have dealt with different topics regarding the pandemic linked to COVID-19. Objectives: Aim of this paper is to compare the number of deaths attributable to COVID-19, that occurred in the different Italian macro-areas, in the different pandemic waves;we studied the trend of the curves relating to the proportion of deaths to the number of infected in the Italian macro-areas for the pandemic waves and analysed the mortality data, focusing on the Italian context and comparing it with other foreign countries. We examined the data regarding swabs, hospitalizations, home isolation, admissions to intensive care and deaths registered in pandemic period. Results: Geographically, Italy was differently affected by the pandemic. Northern Italy was the most affected area. In comparison with some foreign countries, Italy is one of the nations that paid the most in terms of deaths, due to: delays in understanding the seriousness of the emergency;the slow management in the tracking systems of contagions;the high number of hospitalizations;a corporate organizational system poorly planned. Conclusion: The years 2020 and 2021 have been dramatic and unprecedented. The year 2021 was the year of redemption, where, despite social, economic and health difficulties, thanks to mass vaccination, we were able to give a real strong response to the pandemic. Trust in science has led to a drastic decrease in mortality throughout the world.

关键词： Statistical Analysis Comparisons Swabs Hospitalizations Death Rates

Hybrid Professionals and Academic Productivity: The Case of the University Polyclinic in Messina (Sicily)

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Health 2021年第1期13卷 1-15页

作者： angela alibrandi Lara Gitto Michele Limosani Guido Noto Dipartimento di Economia Università degli Studi di Messina Messina Italy

The productivity of medical staff within a polyclinic is not an easy task due to the multiple activities that physicians must perform at the same time: not only healthcare for patients, but also academic activities, such as scientific research and teaching. Hybrid professionals are healthcare professionals who have to play multiple roles, often not precisely identified. This analysis examines the case study of the University Polyclinic of Messina (Italy) where three university departments and 7 Dipartimenti di Attività Integrate (DAI) are distinguished and physicians (both professors and researchers) are called to reconcile multiple tasks. Given the distinction between university departments and DAIs, the aim of this contribution is to identify the organizational elements that prove to be predictors of scientific efficiency and productivity. To what extent does the inclusion in a DAI or within a university department affect individual incentives? A new dataset is built for the present research containing information on University Polyclinic of Messina physicians (full professors, associate professors, researchers). From the Scopus online database (https://***/***) individual information relating to the number of publications, the number of citations, h-index was obtained. The latter is used to assess the quality of individual research;in order to evaluate the teaching activity, the number of hours dedicated to didactical activities is taken into account, together with the number of teaching hours required by one’s role. Information related to remuneration and the circumstance of carrying out intramural activities has also been included. A thorough statistical analysis is carried out and the individual groups (DAI and university departments) are compared through the Kruskal Wallis test. Estimating a Poisson Gamma mixture model highlights those variables that are significant predictors of scientific product

关键词： Hybrid Professionals University Departments DAI h-Index Poisson-Gamma Mixture Model

Market Analysis of Typical Products in Italy： Bivariate Statistical Relationships Between Qualitative Variables

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Chinese Business Review 2012年第1期11卷 65-74页

作者： Lanfranchi Maurizio Giannetto Carlo Zirilli Agata alibrandi angela Messina University Messina Italy

The denominations of origin being perceived by the consumers in terms of both intrinsic qualities and of extrinsic qualities, have contributed in no uncertain manner to the increase of the typical products in question, positively influenced also by the noted emergencies coming from verified alimentary alarms during the beginning of the XXI century. The objective of this paper, is to determine the habits of purchase of typical and traditional products of the people of Messina （Sicily, Italy）. To do this a ＂motivational＂ survey was carried out by traditional methodology of descriptive researches. The adopted methodology of research was quantitative and random. The random research strives to identify the factors that depend on the behaviour of purchase and the appraisal of the existing relationships of cause-effect in a determined population. The interviewed were given a questionnaire composed of 17 questions on their knowledge of the typical products characteristics, the frequency of consumption, the monthly amounts destined to the purchase, the motivations that push them to the purchase of typical products rather than pre-packed. Methodologically, our statistical analysis has been performed using the log-likelihood ratio test in order to investigate the existence of association between the joint distributions of qualitative measured variables.

关键词： typical products market analysis statistical analysis log-likelihood ratio test

High circulating D-dimers are associated with ascites and hepatocellular carcinoma in liver cirrhosis

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World Journal of Gastroenterology 2008年第10期14卷 1549-1552页

作者： Aldo Spadaro Vincenza Tortorella Carmela Morace Agostino Fortiguerra Paola Composto Caterina Bonfiglio angela alibrandi Carmelo Luigiano Giuseppe De Caro Antonino Ajello Oscar Ferraù Maria Antonietta Freni Department of Medicine and Pharmacology University Hospital Messina 98125 Italy Department of Statistics University oMessina Messina 98125 Italy

AIM: To measure plasma D-dimer levels in cirrhotic patients with and without ascites, assessing the effect of ascites resolution in D-dimer concentration. METHODS: Seventy consecutive cirrhotic patients (M = 44, F = 26, mean age 65 years, SD ± 13), observed from October 2005 to March 2006 were enrolled. Circulating D-dimer levels were measured using a latex-enhanced, immunoturbidimetric test. In patients with ascites (n = 42) the test was repeated after ascites resolution. RESULTS: Ascites was present in 42 patients (group A) and absent in 28 (group B). Group A patients had more advanced liver disease. Hepatocellular carcinoma (HCC) was diagnosed in 14 patients and was more frequent in group B. Above normal range D-dimers were found in 45/70 patients. High D-dimers were more frequent in group A than in group B (P = 0.001). High D-dimers were associated with presence of HCC (P = 0.048) only in group B. After ascites resolution, obtained in all patients, mean D-dimer values decreased in those 34 patients with high basal levels (P = 0.007), returning to normal in 17. CONCLUSION: In patients with liver cirrhosis, ascites and HCC are the main factors associated with increased fibrinolytic activity.

关键词： D-dimers Liver cirrhosis Ascites Hepatocellular carcinoma Hyperfibrinolysis

Low utility of plasma Nociceptin/orphanin FQ in the diagnosis of hepatocellular carcinoma

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World Journal of Gastroenterology 2006年第29期12卷 4716-4720页

作者： Aldo Spadaro Antonino Ajello Carmelo Luigiano Carmela Morace Maria Letizia Resta Grazia Berlinghieri Salvatore Campo Claudio Scisca angela alibrandi Graziella D'arrigo Nunziata Alessi Oscar Ferraù Maria Antonietta Freni Dipartimento Clinico Sperimentale di Medicina e Farmacologia Clinica Medica Pad.CAOUVia Consolare Valeria No.1Messina 98125Italy

AIM： The utility of serum alpha-fetoprotein （α-FP） in the detection of hepatocellular carcinoma （HCC） is questionable. Very high circulating levels of nociceptin/ orphanin FQ （N/OFQ）, a ligand for a novel opioid receptor, have recently been reported in HCC. The aim of this study was to assess the role of plasma N/OFQ in the diagnosis of HCC arising in patients with liver cirrhosis. METHODS： Plasma N/OFQ levels were measured by ELISA in 58 patients （28 HCC and 30 liver cirrhosis） and in 25 healthy controls. The values were correlated with clinical and laboratory features including α-FP. Spearman index, biserial correlation coefficient, non parametric combination （NPC） test and discriminant stepwise analysis were used for statistical evaluation of data.RESULTS： The upper normal limit of nociceptin was 122 pg/mL. Plasma levels above this cut-off were found in 21.4% of patients with HCC, in 23.3% of those with cirrhosis and in 8% of healthy subjects. α-FP serum levels〉200 ng/mL were found in 46.4% of the patients with HCC and in none of those with cirrhosis. No correlation was found between N/OFQ levels and any of the clinical and laboratory features, including α-FP. By NPC test, HCC and cirrhotic patients were different with regard to α-FP （P = 0.000） but not in terms of nociceptin （P = 0.595）. By point biserial correlation, HCC presence was positively correlated with α-FP （rpb = 0.52, P = 0.000） but not with N/OFQ （rpb = 0.16, P = 0.157）. In a discriminant analysis, α-FP was significant in the Wilks test （Y = -0.709 ＋ 0.03 α-FP） and properly classified 81% of all patients and 61% of HCC. N/OFQ had lower sensitivity, specificity and predictive values than α-FP. CONCLUSION： Nociceptin is increased in patients with chronic liver disease, independently of the presence of HCC, although the underlying mechanism has yet to be clarified. We conclude it is not a useful marker for HCC.

关键词： Hepatocellular carcinoma Nociceptin/orphanin FQ Liver cirrhosis Alpha-fetoprotein