Search Results

1 - 10 of 118 items :

  • "Mann-Whitney test" x
Clear All

Summary

This paper discusses the problem of determining the number of observations necessary to apply the nonparametric Mann-Whitney test. We describe the method given by Noether (1987) for determining a sample size which guarantees that the Mann-Whitney test at a given significance level α has a predetermined power 1-β. The presented theory is tested by calculating the empirical power in computer simulations. The paper also raises the issue of the method of rounding the determined sample size to an even number when the sample is divided into two equinumerous subsamples.

. https://doi.org/10.1186/s12874-015-0023-0 [4] Fagerland, M. W. (2012). t-tests, non-parametric tests, and large studies—a paradox of statistical practice?. BMC Medical Research Methodology, 12(1), 78. https://doi.org/10.1186/1471-2288-12-78 [5] Fagerland, M. W., & Sandvik, L. (2009). Performance of five two-sample location tests for skewed distributions with unequal variances. Contemporary clinical trials, 30(5), 490-496. https://doi.org/10.1016/j.cct.2009.06.007 [6] Fagerland, M. W., & Sandvik, L. (2009). The wilcoxon–mann–whitney test under scrutiny

Abstract

In the present study, trends and variations in climatic variables (i.e. rainfall, wet day frequency, surface temperature, diurnal temperature, cloud cover, and reference and potential evapotranspiration) were analyzed on seasonal (monsoon and non-monsoon) and annual time scales for the Ajmer District of Rajasthan, India. This was done using non-parametric statistical techniques, i.e. the Mann–Kendall (MK) and Modified Mann–Kendall (MMK) tests, over a period of 100 years. The MK test with prewhitening (MK–PW) of climatic series was also applied to climatic variables and the results were compared to those obtained through the MK and MMK tests in order to assess the performance of trend detection methods. The Pettitt–Mann–Whitney (PMW) test was applied to detect the temporal shift in climatic series. The trend analysis revealed that annual and seasonal rainfall did not show any statistically significant trend at a 10% significant level. A noticeable trend increase was found in wet day frequency, surface temperature and reference evapotranspiration (ET) during the non-monsoon season from the three non-parametric statistical tests at a 10% significance level. A statistically significant decrease in maximum temperature was found during the non-monsoon season by the MK–PW test alone. This analysis of several climatic variables at the district scale is helpful for the planning and management of water resources and the development of adaptation strategies in adverse climatic conditions.

p < 0.05). Therefore, counts (frequencies) and percentages were calculated for all QSU variables, but age and experience in kickboxing. The differences between genders were established by the Mann-Whitney test (for non-parametric variables such as “Educational level”, “Competitive achievement”), and independent samples t-tests (for parametric variables, such as KSN, KD, task- and ego-orientation). Multinomial logistic regression models were employed to examine how variables derived by the QSU, KSN, KD and CTEOSQ were associated with the potential doping behavior

Abstract

Introduction: The aim of this study was to evaluate the following parameters of fetuses and neonates with omphalocele: the prevalence of coexisting congenital heart defects (CHD), abnormalities in heart function and the impact of coexisting CHD on fetal and neonatal survival. Material and methods: The study group consisted of 69 fetuses with omphalocele diagnosed and monitored at the Department of Prenatal Cardiology in our Institute in the years 2007-2017. The retrospective analisis of patients' data was performed. For statistical analysis we used Chi-square test, t-Student test and U Mann-Whitney test.. Results: In the studied group omphalocele was an isolated defect in 31.9% of the cases (22/69), in 68.1% (47/69) coexisting defects were present, in 49.3% (34/69) the coexisting defect was CHD. The most common CHD coexisting with omphalocele were ventricular septal defect (VSD), double outlet right ventricle (DORV) and atrio-ventricular septal defect (AVSD). Abnormalities of heart function were present in 43.5% (30/69) of fetuses with omphalocele: 23.5% (8/34) with normal heart anatomy and in 62.9% (22/35) with CHD. Statistically significant differences between the group with normal heart anatomy and the group with CHD regarded: Cardiovascular Profile Score (CVPS) (median 10 points vs median 9 points, U Mann-Whitney test p=0.034), neonatal birth weight(mean 3253 g vs median 2700 g, U Mann-Whitney test p=0.003), Apgar score (median 8 vs median 7, U Mann-Whitney test p=0.038) and survival rate until discharge from hospital (85% vs 52.9%, Chi-square test p=0.034). The comparison of data from 2007-2017 with data obtained from similar analysis performed in our center in 1999-2006, revealed significant improvement in the early detection of omphalocele (median 14.5 weeks of gestation vs mean 25.4 weeks of gestation), gestational age of delivery (mean 38 weeks of gestation vs mean 34 weeks of gestation) and survival rate until discharge both in neonates with normal heart anatomy and coexisting CHD (85% and 52.9% vs 70% and 23% respectively) . Conclusions: 1. The presence of coexisting CHD is an important prognostic factor in fetuses and neonates with omphalocele, so early fetal echocardiography should be performed in every case of omphalocele. 2. During the last decade (2007-2017), in contrast to years 1999-2006, we observed significant improvement in early and complete prenatal diagnosis of omphalocele. 3. We observed improvement in strategy of obstetrical management resulting in delivering neonates in a more advanced gestational age both in the group with normal heart anatomy and the group with coexisting CHD.

Abstract

The paper is a report of the examination of the tribological wear characteristics of certain dental metal biomaterials. In the study, tests were undertaken on the following materials: 316L steel, NiCrMo alloy, technically pure titanium (ASTM-grade 2) and Ti6Al4V ELI alloy (ASTM-grade 5). The tribological tests were performed in artificial saliva to determine the coefficient of friction and wear factor; the traces of wear were then ascertained through SEM. The significance of variations in the wear factor, was subsequently assessed by the U Mann-Whitney test. The resistance to wear in the ball-on-disc test under in vitro conditions was observed for the tested materials in the following order: NiCrMo>316L>Ti6Al4V>Ti grade 2.

Evaluation of Postural Asymmetry and Gross Joint Mobility in Elite Female Volleyball Athletes

The purpose of the study was to evaluate marked postural asymmetry and gross joint mobility in elite female volleyball athletes.

Sixty-two Czech and Slovak elite female volleyball athletes (age 20.7±2.03 years, body mass 71.1±6.18 kg, body height 1.804±.0618 m, BMI 21.8±1.78) were examined by an experienced rehabilitation physician. The set of tests included the frontal posture gross examination, the forward bending test from the standing position and the deep squat test. The spiking hand and the presence of any lower extremity injury were estimated by interview. The proportion test, Mann-Whitney test and t-test were used to evaluate statistical significance (p<0.05).

Fifty subjects (80.6%) exhibited "typical" frontal plane posture in which the acromion, scapula and the iliac crest were in a higher position on the left side than on the right, significantly more frequently than all the other patterns (proportion test, p<0.0001). Ninety-eight percent of the subjects with the "LLL pattern" preferred the right arm for spiking (proportion test, p<0.0001). Forty-one subjects (66%) exhibited hypermobility in the forward bending test, significantly more frequently than twenty-one subjects (34%) with normal results (proportion test, p=0.0003). Thirty-four subjects (55%) did not succeed in the deep squat test and hypermobility in the forward bending test paradoxically prevailed in them significantly (proportion test, p=0.004). Restriction in the deep squat test was not linked to obesity, age (t-test, p=0.081) nor knee (proportion test, p=0.85) and ankle injury (Mann-Whitney test, p=0.36) in the past. Significant prevalence of hypermobility in the forward bending test was not surprising because of general body composition and the performance of regular stretching exercises in elite female volleyball athletes. On the other hand, surprisingly, more than half of the subjects did not succeed in the deep squat test. The cause of poor results in the deep squat test could be due to the tightness of the soleus muscle suffering from chronic overloading and/or an inappropriate stretching methods. An inappropriate and/or insufficient compensatory exercise and stretching method or system could be the cause of their marked postural asymmetry as well.

A detailed examination of posture and muscle imbalance performed by an experienced physician or physiotherapist as well as individually tailored compensatory exercises and a stretching system can be strongly recommended to all elite athletes, not only to volleyball players.

Abstract

Background: With the aim of encouraging mobility between higher education institutions in the Western Balkan countries and those in the European Union (EU), the European Commission initiated a series of measures to increase the share of students primarily from the Western Balkans who spend at least one semester away from their home institutions, but also the share of young people from EU member states who come to Western Balkan (WB) countries. Objectives: Aim of the paper is to determine the degree of representation of internationalisation strategy and policy elements in the internal documents of higher education institutions and its direct impact on the development of mobility. Methods/Approach: An electronic survey has been created and sent to representatives of 9 EU and 11 WB universities. Respondents were mainly international relations officers or management representatives. Mann-Whitney test was applied in order to test differences between EU and WB universities. Results: The conducted Mann-Whitney nonparametric tests show that the degree of representation of internationalisation strategy and policy elements in the internal documents of a higher education institution has a direct impact on the development of mobility. Conclusions: By 2020, the European Commission aims to have 20% of all students acquiring an academic degree within the European Higher Education Area participate in mobility. This paper sheds light on this segment and indicates possible directions for actions aimed at developing mobility at institutions in Western Balkan countries

Abstract

Background: For many years, performance indicators have served as a valid instrument for the evaluation of the public sector quality and efficiency in the majority of developed countries. Such measurements allow internal and external evaluation of the efficiency of the budget and public companies. Objectives: The aim of the paper is to determine to what extent public sector entities in the Federation of Bosnia and Herzegovina (FB&H), as a representative of transition countries, measure and report performance indicators. Methods/Approach: An electronic survey has been conducted among representatives of cantons in FB&H and public utility companies in the Canton of Sarajevo. The Mann-Whitney test was applied in order to test differences between public sector entities according to their performance. Results: The Mann-Whitney non-parametric tests show that the degree of measuring and reporting performance indicators in the public sector in FB&H has a direct impact on the operational results shown in financial statements. Conclusions: EU legislation encourages the development of competition between different programs, products and services in the public sector. This paper sheds light on the causes and consequences of the absence of valid performance measurement in the public sector of FB&H and provides possible solutions to overcome identified problems within measurement, reporting and monitoring of performance indicators.

Summary

Outplacement is a rare HRM tool; hence there is also a lack of research on it. In turn, banks are treated as enterprises that implemented modern management solutions faster than other companies in the countries of Central and Eastern Europe. The bank is a good entity for outplacement testing. Both Poland and Russia belong to the CEE countries. The Polish economy has been promoted to a group of developed countries. The Polish banking sector relies much more on foreign capital than in Russia, which may be important for the development of outplacement. The main aim of this paper is to reveal and explain the differences in the popularity of outplacement in Russian and Polish banks. This article uses survey data collected in Poland and Russia from over 2,000 bank employees. Mann-Whitney test, correlations and discriminant analysis were used. Employees of the Polish banking sector more often than Russian workers noted the absence of any support for dismissed workers (Poland 30%, Russia 23%). Available outplacement forms differentiated in Poland and Russia. A little more focus on counselling support was observed in Poland, and on material support in Russia. The most important factors influencing outplacement were: occupied position, size of locality, sex, work experience in banking, country.