Roberto Vila

ORCID: 0000-0003-1073-0114
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Research Areas
  • Statistical Distribution Estimation and Applications
  • Advanced Statistical Methods and Models
  • Bayesian Methods and Mixture Models
  • Probabilistic and Robust Engineering Design
  • Financial Risk and Volatility Modeling
  • Statistical Methods and Bayesian Inference
  • Statistical Methods and Inference
  • Hydrology and Drought Analysis
  • Probability and Risk Models
  • Theoretical and Computational Physics
  • Stochastic processes and statistical mechanics
  • Reliability and Maintenance Optimization
  • Forecasting Techniques and Applications
  • Fuzzy Systems and Optimization
  • Monetary Policy and Economic Impact
  • Insurance, Mortality, Demography, Risk Management
  • Opinion Dynamics and Social Influence
  • COVID-19 epidemiological studies
  • Markov Chains and Monte Carlo Methods
  • Diverse Scientific and Engineering Research
  • Soil Geostatistics and Mapping
  • Advanced Statistical Process Monitoring
  • Air Quality and Health Impacts
  • Mathematical Dynamics and Fractals
  • Climate variability and models

Universidade de Brasília
2015-2025

Universidade de São Paulo
2025

Universidade Federal de Pernambuco
2025

McMaster University
2023-2024

Departamento de Ciência e Tecnologia
2022

In this paper, we propose a new distribution with unitary support which can be characterized as ratio of the type $W=X_1/(X_1+X_2)$, where $(X_1, X_2)^\top$ follows bivariate extreme Fr\'echet margins, that is, $X_1$ and $X_2$ are two correlated random variables. Some mathematical properties such identifiability, symmetry, stochastic representation, characterization ratio, moments, stress-strength probability, quantiles, maximum likelihood method rigorously analyzed. Two applications discussed.

10.48550/arxiv.2501.00970 preprint EN arXiv (Cornell University) 2025-01-01

Grain producers in Brazil often depend on third-party services for the transportation, processing and storage of their production, as, most part, they do not have silos properties. In this context, efficient logistics is essential to optimize processes increase reliability between customers service providers. This study focuses logistical analysis truck traffic at two grain plants, examining different receiving protocols evaluate internal vehicle flow during peak production conditions. The...

10.17713/ajs.v54i2.1976 article EN cc-by Austrian Journal of Statistics 2025-02-17

Abstract The Birnbaum–Saunders (BS) distribution is a model that frequently appears in the statistical literature and has proved to be very versatile efficient across wide range of applications. However, despite growing interest study this development many articles, few them have considered data with dependency structure. To fill gap, we introduce new class time series models based on BS distribution, which allows modeling positive asymmetric an autoregressive We call these moving average...

10.1002/for.2718 article EN Journal of Forecasting 2020-06-24

Income modeling is crucial in determining workers’ earnings and an important research topic labor economics. Traditional regressions based on normal distributions are statistical models widely applied. However, income data have asymmetric behavior best modeled by non-normal distributions. The objective of this work to propose parametric quantile two distributions: Dagum Singh–Maddala. proposed regression reparameterizations the original inserting a parameter. We present reparameterizations,...

10.3390/math11020448 article EN cc-by Mathematics 2023-01-14

The Gumbel model is a very popular statistical due to its wide applicability for instance in the course of certain survival, environmental, financial or reliability studies. In this work, we have introduced bimodal generalization distribution thatcan be an alternative data. We derive analytical shapes corresponding probability density function and thehazard rate provide graphical illustrations. Furthermore, discussed properties such as mode, bimodality, moment generating moments. Our results...

10.17713/ajs.v52i2.1392 article EN cc-by Austrian Journal of Statistics 2023-03-12

Modelling is challenging topic and using parametric models important stage to reach flexible function for modelling. Weibull distribution has shape scale parameters which play the main role Bimodality parameter added so bimodal can capture real data set with bimodality be actually combination of two populations. The properties proposed estimation method are examined extensively show its usability in modelling accurately safely practitioners. After examination as first issue, it appropriate...

10.1080/02664763.2021.1931822 article EN Journal of Applied Statistics 2021-05-24

We define a new quantile regression model based on reparameterized exponentiated odd log-logistic Weibull distribution, and obtain some of its structural properties. It includes as sub-models known models that can be utilized in many areas. The maximum likelihood method is adopted to estimate the parameters, several simulations are performed study finite sample properties estimators. applicability proposed well justified by means gastric carcinoma dataset.

10.3390/math11061518 article EN cc-by Mathematics 2023-03-21

In this paper, we discuss some theoretical results and properties of the discrete Weibull distribution, which was introduced by Nakagawa Osaki [The distribution. IEEE Trans Reliab. 1975;24:300–301]. We study monotonicity probability mass, survival hazard functions. Moreover, reliability, moments, p-quantiles, entropies order statistics are also studied. consider likelihood-based methods to estimate model parameters based on complete censored samples, derive confidence intervals. two...

10.1080/02331888.2018.1550645 article EN Statistics 2018-11-26

In this paper, we propose a bimodal gamma distribution using quadratic transformation based on the alpha-skew-normal model. We discuss several properties of such as mean, variance, moments, hazard rate and entropy measures. Further, new regression model with censored data distribution. This can be very useful to analysis real could give more realistic fits than other special models. Monte Carlo simulations were performed check bias in maximum likelihood estimation. The proposed models are...

10.1080/02331888.2020.1764560 article EN Statistics 2020-05-03

The modality is an important topic for modelling. Using parametric models efficient way when real data set shows trimodality. In this paper, we propose a new class of trimodal probability distributions, that is, distributions have up to three modes. Trimodality itself achieved by applying proper transformation density function certain continuous distributions. At first, obtain preliminary results arbitrary g(x) and, next, focus on the Gaussian case, studying model more deeply. distribution...

10.1080/02664763.2023.2207785 article EN Journal of Applied Statistics 2023-05-08

We construct a new partially linear regression based on reparametrized generalized gamma distribution with two systematic components that can be easily interpreted. Its parameters are estimated by penalized maximum likelihood. For different parameter settings, sample sizes, and censoring percentages, some simulations performed to examine the accuracy of likelihood estimators, empirical residuals compared standard normal distribution. The methodology is applied breast cancer data in city João...

10.1080/02664763.2024.2337086 article EN Journal of Applied Statistics 2024-04-02

In this article, using inverse integral transforms, we derive the exact distribution of random variable X that is involved in ratio Z=dX/(X+Y) where and Y are independent variables having same support, Z have known distributions. We introduce new distributions way. As an application obtained results, several examples presented.

10.1080/03610926.2024.2340608 article EN Communication in Statistics- Theory and Methods 2024-04-18

ABSTRACT In this paper, we propose and investigate closed‐form point estimators for a weighted exponential family. We also develop bias‐reduced version of these proposed through bootstrap methods. Estimators are assessed using Monte Carlo simulation, revealing favourable results the estimators. illustrate methodology with use two real data sets.

10.1002/sta4.723 article EN Stat 2024-08-27

This paper introduces bivariate log-symmetric models for analyzing the relationship between two variables, assuming a family of distributions. These offer greater flexibility than lognormal distribution, allowing better representation diverse distribution shapes and behaviors in data. The is widely used various scientific fields includes distributions such as log-normal, log-Student-t, log-Laplace, among others, providing several options modeling different data types. However, there are few...

10.3390/sym16101315 article EN Symmetry 2024-10-05

This work aims to study the factors that increase risk of death hospitalized patients diagnosed with COVID-19 through odd log-logistic regression model for censored data two systematic components, as well provide new mathematical properties this distribution. To achieve this, a dataset individuals residing in city Campinas (Brazil) was used and simulations were performed investigate accuracy maximum likelihood estimators proposed model. The provided properties, such stochastic...

10.3390/math10193644 article EN cc-by Mathematics 2022-10-05

10.1007/s10651-023-00566-7 article EN Environmental and Ecological Statistics 2023-06-01

We define a four-parameter extended Rayleigh distribution which is quite flexible model to analyze positive data, and includes as special models the odd log-logistic generalized Rayleigh, exponentiated distributions.We obtain linear representation some of its mathematical properties.We construct regression from new with two systematic components for censored data.The estimation done by maximum likelihood.The utility proved in real applications.

10.32372/chjs.14-01-01 article EN Chilean Journal of Statistics 2023-06-30

We use the Clayton and Frank copulas exponentiated odd log-logistic family to define a new flexible bivariate model fit bimodal asymmetry data. The allow different distributions for response variable, thus making analysis more suitable. present some structural properties of describe simulation study show consistency estimators. construct regression based on oak lettuce plant data concentrations silicon dioxide organosilicon compounds. check variables fresh weight height together in order...

10.3390/sym15091778 article EN Symmetry 2023-09-18
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