Search results for "multivariate statistic"
showing 10 items of 327 documents
Unveiling the Relationship Between Sea Surface Hydrographic Patterns and Tuna Larval Distribution in the Central Mediterranean Sea
2021
Thunnus thynnus (Atlantic bluefin tuna, ABT) and other tuna species reproduce in the Mediterranean Sea during the summer period. Despite the Central Mediterranean Sea, the Strait of Sicily in particular, being a key spawning site for many tuna species, little is known on the effects of oceanographic variability on their larval distribution in this area. The abundance and presence-absence of larval specimens for three tuna species (ABT, bullet tuna and albacore) were modeled in order to examine their relationships with environmental factors, by analysing historical in situ information collected during seven annual surveys (2010–2016). The results revealed that most tuna larvae for the three …
THE ROLE OF SUNK COSTS IN THE DECISION TO INVEST IN R&D
2009
We present a dynamic empirical model of a firm's R&D decisions that is consistent with the existence of sunk R&D costs, taking into account that these costs may differ between small and large firms, and among different technological regimes. We estimate a multivariate dynamic discrete choice model using firm-level data of Spanish manufacturing for 1990–2000. Conditional on firm heterogeneity and serially correlated unobservable factors, we find that R&D history matters. This true state dependence allows inferring the existence of sunk R&D costs associated with performing R&D. Sunk R&D costs are found to be higher for large, high-tech firms.
Docking and multivariate methods to explore HIV-1 drug-resistance: a comparative analysis
2007
In this paper we describe a comparative analysis between multivariate and docking methods in the study of the drug resistance to the reverse transcriptase and the protease inhibitors. In our early papers we developed a simple but efficient method to evaluate the features of compounds that are less likely to trigger resistance or are effective against mutant HIV strains, using the multivariate statistical procedures PCA and DA. In the attempt to create a more solid background for the prediction of susceptibility or resistance, we carried out a comparative analysis between our previous multivariate approach and molecular docking study. The intent of this paper is not only to find further supp…
Study of the microstructure and efficiency of YSZ-SPS finely structured ceramic coatings
2018
Thanks to the using of liquid carrier, suspension plasma spray (SPS) enables the manufacture of finely structured coatings. As for conventional plasma spraying (APS), the microstructures of SPS coatings can be tailored by controlling the spray conditions. However, SPS is more complicated than APS due to its number of modifiable parameters.This thesis aims to provide a more fundamental understanding of the relationship between SPS process parameters and the properties of YSZ coatings by identifying generic models based on the use of mathematical statistical methods for the study of influence and sensitivity of the individual parameters.Systematic experiments were carried out to study the inf…
A statistical approach towards a regionalization of daily rainfall in Sri Lanka
1993
Regionalization of daily rainfall in Sri Lanka was examined using orthogonal factor analysis (OFA) based on daily rainfall data of 42 stations for a 15-year period (1971–1985). The number of potential rainy days was computed from the original data matrix and subjected to S-mode OFA. The first 10 orthogonal factors were shown as highly significant, explaining 65.1 per cent of the total variance of the whole data matrix, where the level of eigenvalues represented was > 1.0. Noticeably, the 10 orthogonal factors clearly revealed the different homogeneous daily rainfall regions in Sri Lanka (labelled as A to J), according to the orthogonal factor high loadings matrix. Delimitation of the daily …
Multivariate nonparametric tests in a randomized complete block design
2003
AbstractIn this paper multivariate extensions of the Friedman and Page tests for the comparison of several treatments are introduced. Related unadjusted and adjusted treatment effect estimates for the multivariate response variable are also found and their properties discussed. The test statistics and estimates are analogous to the traditional univariate methods. In test constructions, the univariate ranks are replaced by multivariate spatial ranks (J. Nonparam. Statist. 5 (1995) 201). Asymptotic theory is developed to provide approximations for the limiting distributions of the test statistics and estimates. Limiting efficiencies of the tests and treatment effect estimates are found in the…
Diagnosis of damage to Norway spruce (Picea abies) through biochemical criteria
1995
Bioindication can be carried out at different hierarchical levels, eg. cell, organism, and ecosystem. While the monitoring of damage by visible criteria (e.g. loss of needles) is connected with the organism as a whole, the monitoring of damage by biochemical indicators is above all connected with cell metabolism. The degree of vitality of a tree can be ascertained through the integration of a number of biochemical parameters. Furthermore, a differential diagnosis of a particular stress pattern can be carried out because of the feedback pattern of several biochemical indicators. In order to describe and interpret biochemical or physiological changes that have been caused by a number of facto…
Multivariate factor analysis of Girgentana goat milk composition
2005
The interpretation of the several variables that contribute to defining milk quality is difficult due to the high degree of correlation among them. In this case, one of the best methods of statistical processing is factor analysis, which belongs to the multivariate groups; for our study this particular statistical approach was employed. A total of 1485 individual goat milk samples from 117 Girgentana goats, were collected fortnightly from January to July, and analysed for physical and chemical composition, and clotting properties. Milk pH and tritable acidity were within the normal range for fresh goat milk. Morning milk yield resulted 704 ± 323 g with 3.93 ± 1.23% and 3.…
Influence Functions and Efficiencies of k-Step Hettmansperger–Randles Estimators for Multivariate Location and Regression
2016
In Hettmansperger and Randles (Biometrika 89:851–860, 2002) spatial sign vectors were used to derive simultaneous estimators of multivariate location and shape. Oja (Multivariate nonparametric methods with R. Springer, New York, 2010) proposed a similar approach for the multivariate linear regression case. These estimators are highly robust and have under general assumptions a joint limiting multinormal distribution. The estimates are easy to compute using fixed-point algorithms. There are however no exact proofs for the convergence of these algorithms. The existence and uniqueness of the solutions also still remain unproven although we believe that they hold under general conditions. To ci…
The Age-Participation Relationship Revised: Focus on Older Adults
1998
This study aims to increase our understanding of how the negative influence of age on participation comes about. The framework used emphasizes human life complexity and human agency in behavior and decision-making. Accordingly, main effects and multiple interaction effects of age and some education and work-related factors on participation were examined. The results show that when the interaction effects are taken into account, the age-participation relationship becomes more complex than previously found in studies focusing only on main effects. It is suggested that research on participation utilize the more advanced options available in multivariate statistics and thus aim at better compa…