Search results for "Univariate"

Multivariate Nonparametric Tests

2004

Multivariate nonparametric statistical tests of hypotheses are described for the one-sample location problem, the several-sample location problem and the problem of testing independence between pairs of vectors. These methods are based on affine-invariant spatial sign and spatial rank vectors. They provide affine-invariant multivariate generalizations of the univariate sign test, signed-rank test, Wilcoxon rank sum test, Kruskal–Wallis test, and the Kendall and Spearman correlation tests. While the emphasis is on tests of hypotheses, certain references to associated affine-equivariant estimators are included. Pitman asymptotic efficiencies demonstrate the excellent performance of these meth…

Efficient Estimation of Non-Linear Finite Population Parameters by Using Non-Parametrics

2013

Summary Currently, high precision estimation of non-linear parameters such as Gini indices, low income proportions or other measures of inequality is particularly crucial. We propose a general class of estimators for such parameters that take into account univariate auxiliary information assumed to be known for every unit in the population. Through a non-parametric model-assisted approach, we construct a unique system of survey weights that can be used to estimate any non-linear parameter that is associated with any study variable of the survey, using a plug-in principle. Based on a rigorous functional approach and a linearization principle, the asymptotic variance of the estimators propose…

Seeing Univariate Data

2011

Digital generation of multivariate wind field processes

2001

Abstract A very efficient procedure for the generation of multivariate wind velocity stochastic processes by wave superposition as well as autoregressive time series is proposed in this paper. The procedure starts by decomposing the wind velocity field into a summation of fully coherent independent vector processes using the frequency dependent eigenvectors of the Power Spectral Density matrix. It is shown that the application of the method allows to show some very interesting physical properties that allow to reduce drastically the computational effort. Moreover, using a standard finite element procedure for approximating the frequency dependent eigenvectors, the generation procedure requi…

Univariate and multivariate statistical aspects of equity volatility

2004

We discuss univariate and multivariate statistical properties of volatility time series of equities traded in a financial market. Specifically, (i) we introduce a two-region stochastic volatility model able to well describe the unconditional pdf of volatility in a wide range of values and (ii) we quantify the stability of the results of a correlation-based clustering procedure applied to synchronous time evolution of a set of volatility time series.

Factors selection in landslide susceptibility modelling on large scale following the gis matrix method: application to the river Beiro basin (Spain)

2012

A procedure to select the controlling factors connected to the slope instability has been defined. It allowed us to assess the landslide susceptibility in the Rio Beiro basin (about 10 km2) over the northeastern area of the city of Granada (Spain). Field and remote (Google EarthTM) recognition techniques allowed us to generate a landslide inventory consisting in 127 phenomena. To discriminate between stable and unstable conditions, a diagnostic area had been chosen as the one limited to the crown and the toe of the scarp of the landslide. 15 controlling or determining factors have been defined considering topographic, geologic, geomorphologic and pedologic available data. Univariate tests, …

Worse recent efficacy of antiviral therapy in liver transplant recipients with recurrent hepatitis C: Impact of donor age and baseline cirrhosis

2009

We hypothesized that antiviral efficacy [sustained virologic response (SVR)] has improved in recent years in the transplant setting. Our aim was to assess whether the efficacy of pegylated interferon (PegIFN)–ribavirin (Rbv) has improved over time. One hundred seven liver transplant patients [74% men, 55.5 years old (range: 37.5–69.5), 86% genotype 1a or 1b] were treated with PegIFN-Rbv for 355 (16–623) days at 20.1 (1.7–132.6) months after transplantation. Tacrolimus was used in 61%. Sixty-seven percent had baseline F3–F4 (cirrhosis: 20.5%). Donor age was 49 (12–78) years. SVR was achieved in 39 (36.5%) patients, with worse results achieved in recent years (2001–2003: n = 27, 46.5%; 2004: …

The exact distribution of a weighted Convolution of two Gamma distributions

2006

Si considera una rappresentazione della funzione di densit`a di probabilit`a di una Convoluzione ponderata di distribuzioni Gamma, in cui una funzione ipergeometrica confluente descrive come le differenze tra i parametri di scala delle componenti determinino allontanamenti da una densit`a Gamma. Si considera il caso specifico di una convoluzione di due variabili gamma per mostrare, come al vantaggio interpretativo si aggiunga la possibilit`a di derivare in forma esplicita e computazionalmente semplice, espressioni della funzione di ripartizione e dei momenti. Si mostra la relazione tra tale distribuzione ed il sistema delle distribuzioni di Bessel, e si generalizza inoltre al caso di convol…

Einfluß der Proliferationsrate auf den Krankheitsverlauf von nodalnegativen Mammakarzinomen

1995

In 250 patients with node-negative breast cancer and no systemic adjuvant therapy the impact on the prognosis of the variables age, histological tumour type, tumour size, histological grade, receptor status and localisation of the tumour within the breast, was studied. Patients were followed over a mean period of 60 (range 7-164) months. In a subset of 124 cases additional examination of the growth fraction rate, detected by immunohistochemical determination of antibody Ki-67 and semiquantitative measurement of the stained tumour cell nuclei was performed. In 43 cases, measurement of S-phase fraction by flow cytometry was also performed. By univariate analysis, the histological tumour type …

Histological features and ki-67 index in cervical atypical lesions

2008

One of the most frequent challenges in routine diagnostic assessment of cervical biopsies consists of some lesions in which histological features of HPV infection are either inconsistently present or only mildly/focally evident. We named them Atypical Lesions (AL) because differential diagnosis with metaplastic/reactive lesions and LSIL is difficult. It would be important to identify among them those lesions that are really HPV-associated. We studied 52 AL cases to evaluate whether the morphological features and the proliferation index, assessed by Mib1 (Ki67) immunostaining, would be useful to better understand the real nature of AL, with relation to the HPV presence and to the proliferati…