Search results for "Multivariate Analysi"
showing 10 items of 1084 documents
Uncertainty evaluation of design rainfall for urban flood risk analysis
2011
A reliable and long dataset describing urban flood locations, volumes and depths would be an ideal prerequisite for assessing flood frequency distributions. However, data are often piecemeal and long-term hydraulic modelling is often adopted to estimate floods from historical rainfall series. Long-term modelling approaches are time- and resource-consuming, and synthetically designed rainfalls are often used to estimate flood frequencies. The present paper aimsto assess the uncertainty of such an approach and for suggesting improvements in thedefinition of synthetic rainfall data for flooding frequency analysis. According to this aim, a multivariate statistical analysis based on a copulameth…
Serological prevalence of toxoplasmosis in pregnant women in Luanda (Angola): Geospatial distribution and its association with socio-demographic and …
2020
We report a study on toxoplasmosis in pregnant women in Luanda, Angola, determining the seroprevalence, geospatial distribution and its association with socio-economic features, dietary habits and hygiene and health conditions. Anti-Toxoplasma gondii IgG and IgM were quantified in serum samples of women attended at the Lucrecia Paim Maternity Hospital between May 2016 and August 2017. The IgG avidity test and qPCR assay were used for dating the primary infection. Data were collected by questionnaire after written consent, and spatial distribution was assessed through a Kernel Density Function. The potential risk factors associated with Toxoplasma infection were evaluated using bivariate and…
Assessment of the statistical significance of classifications in infrared spectroscopy based diagnostic models.
2014
Fourier transform infrared (IR) spectroscopy in combination with multivariate data analysis is a versatile tool that can be applied to disease diagnosis. However, a rigorous validation of the obtained models is necessary in order to obtain robust results. This work evaluates the advantages of the use of permutation testing for determining the statistical significance of the misclassification errors obtained from IR based diagnostic models through cross validation (CV). The model performance, estimated by CV, is compared to a distribution of CV-performance values obtained using randomly permuted class labels. The distribution of ‘random CV-values’ is considered as a null distribution and use…
T-pattern analysis for the study of temporal structure of animal and human behavior : a comprehensive review
2014
A basic tenet in the realm of modern behavioral sciences is that behavior consists of patterns in time. For this reason, investigations of behavior deal with sequences that are not easily perceivable by the unaided observer. This problem calls for improved means of detection, data handling and analysis. This review focuses on the analysis of the temporal structure of behavior carried out by means of a multivariate approach known as T-pattern analysis. Using this technique, recurring sequences of behavioral events, usually hard to detect, can be unveiled and carefully described. T-pattern analysis has been successfully applied in the study of various aspects of human or animal behavior such …
Optional Learning Opportunities
2018
The effects of offering and seizing optional learning opportunities rarely have been investigated. Thus, university instructors have no basis on which to decide whether offering optional learning opportunities to their students would be worth the effort and which students would seize and benefit from them. To target these questions, we designed a teaching−learning format in which we offered psychology undergraduates optional learning opportunities throughout the semester. We investigated the cognitive and motivational prerequisites of N=108 students who seized versus forwent the learning opportunities and compared their learning outcomes both with and without controlling for prerequisites.…
Pretest-Posttest-Posttest Multilevel IRT Modeling of Competence Growth of Students in Higher Education in Germany
2016
Longitudinal research in higher education faces several challenges. Appropriate methods of analyzing competence growth of students are needed to deal with those challenges and thereby obtain valid results. In this article, a pretest-posttest-posttest multivariate multilevel IRT model for repeated measures is introduced which is designed to address educational research questions according to a German research project. In this model, dependencies between repeated observations of the same students are considered not, as usual, by clustering observations within participants but rather by clustering observations within semesters. Estimation of the model is conducted within a Bayesian framework. …
Work stress and health problems of professional drivers: A hazardous formula for their safety outcomes
2018
BackgroundSeveral empirical studies have shown that professional drivers are a vulnerable occupational group, usually exposed to environmental stressors and adverse work conditions. Furthermore, recent studies have associated work-related stress with negative job performances and adverse health outcomes within this occupational group, including cardiovascular diseases and unsafe vehicle operation.ObjectiveThe aim of this study was to describe the working conditions and the health status of this occupational group, and to evaluate the association between the Demand–Control model of job stress and their self-reported health and safety outcomes.MethodsA pooled sample of 3,665 Colombian profess…
Non-Hierarchical Clustering as a method to analyse an open-ended questionnaire on algebraic thinking
2016
The problem of taking a data set and separating it into subgroups, where the members of each subgroup are more similar to each other than they are to members outside the subgroup, has been extensively studied in science and mathematics education research. Student responses to written questions and multiple-choice tests have been characterised and studied using several qualitative and/or quantitative analysis methods. However, there are inherent difficulties in the categorisation of student responses in the case of open-ended questionnaires. Very often, researcher bias means that the categories picked out tend to find the groups of students that the researcher is seeking out. In this paper, …
Multivariate analysis of defensive phase in football: Identification of successful behavior patterns of 2014 Brazil FIFA World Cup
2021
The aim of this study was to identify variables associated with direct recovery of the ball during defensive transitions in elite soccer and to propose a model with certain guarantees of success based on a multivariate analysis in which binary logistic regression was used to explore interaction between variables. 1,722 defensive transitions were analysed in the final stages of the FIFA World Cup 2014 in Brazil and investigated the following variables: duration of defensive transition; possession loss zone; position of players at the start and end of the defensive transitions, defensive organization, general defensive approach, period of the match, position of defence line, zone in which the…
New cut-off criterion for uninformative variable elimination in multivariate calibration of near-infrared spectra for the determination of heroin in …
2008
A new cut-off criterion has been proposed for the selection of uninformative variables prior to chemometric partial least squares (PLS) modelling. After variable elimination, PLS regressions were made and assessed comparing the results with those obtained by PLS models based on the full spectral range. To assess the prediction capabilities, uninformative variable elimination (UVE)-PLS and PLS were applied to diffuse reflectance near-infrared spectra of heroin samples. The application of the proposed new cut-off criterion, based on the t-Students distribution, provided similar predictive capabilities of the PLS models than those obtained using the original criteria based on quantile value. H…