Search results for "Multivariate Analysis"

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…

A Multivariate Analysis on Non-nucleoside HIV-1 Reverse Transcriptase Inhibitors and Resistance Induced by Mutation

2003

This paper describes the use of multivariate statistical procedure PCA as a tool to explore the inhibitory activity of classes of NNRTIs against HIV-1 viruses (wild type and more frequent mutants, Y181C, V106A, K103N, L100I) and against RT enzyme. The analysis of correlations between biological activity and molecular descriptors or similarity indexes allowed a reliable classification of the fifty five derivatives considered in this study. The best results were obtained in the case of L100I and K103N mutants for which the higher number of assignments was found when the principal components derived from the descriptors were used. On this basis this statistical approach is proposed as a reliab…

Geographic variation of the Greater white-toothed shrew (Crocidura russula Hermann, 1780 Mammalia, Soricidae)

1996

A multivariate morphometric study of the Greater white-toothed shrew (C. russula) throughout its Palearctic range was carried out to search for patterns of geographic variation within the species boundary. Burnaby's and multiple group principal component analysis allowed the adjustment of raw data with respect to within-sample allometric variation. Multivariate 'size-free' results show a stepped cline with the phenotypical trait reduction and shape change from the eastern to the western Maghreb. Pleistocene fossil mandibles proved to have low phenetic distances with eastern populations (Tunisia, east Algeria) and it is argued that their character set is the primitive condition. The ancestra…

Perioperative Management of Pheochromocytoma: From a Dogmatic to a Tailored Approach

2021

Background: Perioperative management of pheochromocytoma (PCC) remains under debate. Methods: A bicentric retrospective study was conducted, including all patients who underwent laparoscopic adrenalectomy for PCC from 2000 to 2017. Patients were divided into two groups: Group 1 treated with alpha-blockade, and Group 2, without alfa-blockers. The primary end point was the major complication rate. The secondary end points were: the need for advanced intra-operative hemostasis, the admission to the intensive care unit (ICU), the length of stay (LOS), systolic (SBP), and diastolic blood pressure (DBP). Univariate and multivariate analysis was conducted. A p-value &lt

Investigating the possible impact of peritoneal tumor exposure amongst women with early stage cervical cancer treated with minimally invasive approac…

2021

Abstract Introduction Recent findings show a detrimental impact of the minimally invasive approach on patients with early stage cervical cancer (ECC). Reasons beyond these results are unclear. The aim of the present article is to investigate the possible role of peritoneal contamination during intracorporeal colpotomy. Methods patients with early stage cervical cancer were divided into 2 groups: no intraperitoneal exposure (N-IPE) intraperitoneal exposure (IPE) during minimally invasive surgery. Patients of the 2 groups were propensity-matched according to the major risk factors. Results 226 cases of the IPE group had a significant worst prognosis than the 142 cases of the N-IPE group (4.5-…

A multivariate statistical and relaxometry approach to study the provenance and traceability of dairy products

Psychosocial adjustment in aggressive popular and aggressive rejected adolescents at school+

2014

AbstractThe purpose of the present study was to compare the profiles of aggressive adolescents who differed in social status in the classroom, popular vs. rejected, with those of adolescents of average sociometric status without documented behavior problems. The characteristics compared related to intra-individual, family, school, and social domains. A sample of 457 adolescents, aged 11 to 18 years old (48% girls), participated in the study. Differences between groups were examined via a series of multivariate analyses of variance and discriminant function analyses. Results indicated that although aggressive popular adolescents revealed more academic involvement and social integration in th…

A new look at the meeting clustering effect

2021

PurposeThe study aims to test the existence of a meeting clustering effect in the Spanish Stock Exchange (SSE).Design/methodology/approachThis paper studies the relationship between the clustering of annual general meetings and stock returns in the SSE. A multivariate analysis is carried out in order to analyse the relationship between monthly returns and the clustering of general meetings in the SSE.FindingsThe authors show that meeting clustering exists and that some months exhibit significant and positive additional returns related to the holding of ordinary or extraordinary general meetings.Research limitations/implicationsThe authors have explored some possible explanations for the mee…