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Advances in Regression, Survival Analysis, Extreme Values, Markov Processes and...
da Silva, João Lita; Caeiro, Frederico; Natário, Isabel; Braumann, Carlos A.; Esquível, Manuel L.; Mexia, João TiagoSelected papers of the 17th Congress of the Portuguese Statistical Society, covering recent advances in Statistics, particularly in Regression, Extreme values, Markov processes and statistical applications in several areas.
Models of Symmetric Stochastic Matrices.
Dias, Cristina; Oliveira, Manuela; Mexia, JoãoIn this paper we present models for symmetric stochastic matrices showing how to adjust and validate them. We discuss the validation in the general case
One-way Random Effects ANOVA: An Extension to Samples with Random Size
Nunes, Célia; Ferreira, Dário; Ferreira, Sandra; Oliveira, Manuela; Mexia, JoãoThe aim of this paper is to extend one-way random effects ANOVA to situations in which we can not previously know the sample sizes. In this case it is more appropriate to consider the sample sizes as realizations of random variables. We will obtain the distribution of the F-tests, which has random degrees of freedom for the errors. Moreover we will show the equivalence between two expressions for the F-tests.
MODELLING THE COMPROMISE MATRIX IN STATIS
Areia, Anibal; Oliveira, Manuela; Mexia, JoãoSTATIS methodology has three phases: Inter-structure, Compromise, and Intra-structure. In order to be able to carry out inference and simultaneously study several matched series of studies models were introduced for the first place, e. g. Areia et al. 2008 and Oliveira and Mexia 2007. In this poster we extend the models to the Compromise. We apply our approach to the results of local elections in Mainland Port...
Non-centrality parameter in STATIS interstructure
Inácio, Sónia; Delgado, António; Oliveira, Manuela; Mexia, JoãoStatistical theory of STATIS interstructure relies heavily on F statistic. In this paper we show how to complete the inference working with the non centrality parameters of these statistics. Many times these statistics have very high values and there is an almost overflow of significant results. This lead us to use the non-centrality parameters as measures of relevance for effects and interactions. In the STATI...
Analysis of residuals and adjustment in JRA
Oliveira, Amílcar; Oliveira, Teresa; Mexia, João TiagoJoint Regression Analysis (JRA) is based in linear regression applied to yields, adjusting one linear regression per cultivar. The environmental indexes in JRA correspond to a non observable regressor which measures the productivity of the blocks in the field trials. Usually zig-zag algorithm is used in the adjustment. In this algorithm, minimizations for the regression coefficients...
SPI-based drought category prediction using loglinear models
Moreira, Elsa E.; Coelho, Carlos A.; Paulo, Ana A.; Pereira, L.S.; Mexia, João T.Loglinear modeling for three-dimensional contingency tables was used with data from 14 rainfall stations located in Alentejo and Algarve region, southern of Portugal, for short term prediction of drought severity classes. Loglinear models were fitted to drought class transitions derived from Standardized Precipitation Index (SPI) time series computed in a 12-month time scale. Quasi-association loglinear models ...
Multiple regression models for lactation curves
Pereira, Marta S. P.; Oliveira, Teresa; Mexia, João TiagoSeveral methods have been developed in order to study lactation curves. However, the lactation curves are often not well adjusted since several factors affect milk production. The usual model used to describe a lactation curve is Wood’s Model, which generally uses a logarithmic transformation of an incomplete gamma curve to obtain least squares estimates of three constants: a - a scaling factor associated wit...
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