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Modelos lineares generalizados mistos para dados longitudinais. / Generalized linear mixed models in longitudinal data.Costa, Silvano Cesar da 13 March 2003 (has links)
Experimentos cujas variaveis respostas s~ ao proporcoes ou contagens, sao muito comuns nas diversas areas do conhecimento, principalmente na area agricola. Na analise desses experimentos, utiliza-se a teoria de modelos lineares generalizados, bastante difundida (McCullagh & Nelder, 1989; Demetrio, 2001), em que as respostas sao independentes. Caso a variancia estimada seja maior do que a esperada, estima-se o parametro de dispersao, incluindo-o no processo de estimaçao dos parametros. Quando a variavel resposta e observada ao longo do tempo, pode haver uma correlacao entre as observacoes e isso tem que ser levado em consideracao na estimacao dos parametros. Uma forma de se trabalhar essa correlacao e aplicando a metodologia de equacoes de estimacao generalizada (EEG), discutida por Liang & Zeger (1986), embora, neste caso, o interesse esteja nas estimativas dos efeitos fixos e a inclusao da matriz de correlacao de trabalho sirva para se obter um melhor ajuste. Uma outra alternativa e a inclusao, no preditor linear, de um efeito latente para captar variabilidades nao consideradas no modelo e que podem in uenciar nos resultados. No presente trabalho, usa-se uma forma combinada de efeito aleatorio e parametro de dispersao, incluidos conjuntamente na estimacao dos parametros. Essa metodologia e aplicada a um conjunto de dados obtidos de um experimento com camu-camu, com objetivo de se avaliarem quais os melhores metodos de enxertia e tipos de porta-enxertos que podem ser utilizados, atraves da proporcao de pegamentos da muda. Varios modelos sao ajustados, desde o modelo em parcelas subdivididas (supondo independencia), ate o modelo em que se considera o parametro de dispersao e efeito aleatorio conjuntamente. Ha evidencias de que o modelo em que se inclui o efeito aleatorio e o parametro de dispersao, conjuntamente, resultam em melhores estimativas dos parametros. Outro conjunto de dados longitudinais, com milho transgenico MON810, em que a variavel resposta e o numero de lagartas (Spodoptera frugiperda), e utilizado. Neste caso, devido ao excesso de respostas zero, emprega-se o modelo de regressao Poisson in acionado de zeros (ZIP), alem do modelo Poisson padrao, em que as observacoes sao consideradas independentes, e do modelo Poisson in acionado de zeros com efeito aleatorio. Os resultados mostram que o efeito aleatorio incluido no preditor foi nao significativo e, assim, o modelo adotado e o modelo de regressao Poisson in acionado de zeros. Os resultados foram obtidos usando-se os procedimentos NLMIXED, GENMOD e GPLOT do SAS - Statistical Analysis System, versao 8.2. / Experiments which response variables are proportions or counts are very common in several research areas, specially in the area of agriculture. The theory of generalized linear models, well difused (McCullagh & Nelder, 1989; Demetrio, 2001), is used for analyzing these experiments where the responses are independent. If the estimated variance is greater than the expected variance, the dispersion parameter is estimated including it on the parameter estimation process. When the response variable is observed over time a correlation among observations might occur and it should be taken into account in the parameter estimation. A way of dealing with this correlation is applying the methodology of generalized estimating equations (GEEs) discussed by Liang & Zeger (1986) although, in this case, the interest is on the estimates of the xed efect being the inclusion of a working correlation matrix useful to obtain more accurate estimates. Another alternative is the inclusion of a latent efect in the linear predictor to explain variabilities not considered in the model that might in uence the results. In this work the random efect and the dispersion parameter are combined and included together in the parameter estimation. Such methodology is applied to a data set obtained from an experiment realized with camu-camu to evaluate, through proportion of grafting well successful of seedling, which kind of grafting and understock are suitable to be used. Several models are fitted, since the split plot model (with independence assumption) up to the model where the dispersion parameter and the random efect are considered together. There is evidence that the model including the random efect and the dispersion parameter together, produce better estimates of the parameters. Another longitudinal data set used here comes from an experiment realized with the MON810 transgenic corn where the response variable is the number of caterpillars (Spodoptera frugiperda). In this case, due to the excessive number of zeros obtained, the zero in ated Poisson regression model (ZIP) is used in addition to the standard Poisson model, where observations are considered independent, and the zero in ated Poisson regression model with random efect. The results show that the random efect included in the linear predictor was not significant and, therefore, the adopted model is the zero in ated Poisson regression model. The results were obtained using the procedures NLMIXED, GENMOD and GPLOT available on SAS - Statistical Analysis System, version 8.2.
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Superdispersão em dados binomiais hierárquicos / Overdispersion in hierarchical binomial dataLilian Nati 05 March 2008 (has links)
Para analisar dados binários oriundos de uma estrutura hierárquica com dois níveis (por exemplo, aluno e escola), uma alternativa bastante utilizada é a suposição da distribuição binomial para as unidades experimentais do primeiro nível (aluno) condicionalmente a um efeito aleatório proveniente de uma distribuição normal para as unidades do segundo nível (escola). Neste trabalho, propõe-se a adição de um efeito aleatório normal no primeiro nível de um modelo linear generalizado hierárquico binomial para contemplar uma possível variabilidade extra-binomial decorrente da dependência entre os ensaios de Bernoulli de um mesmo indivíduo. Obtém-se o processo de estimação por máxima verossimilhança para este modelo a partir da verossimilhança marginal dos dados, após uma dupla aplicação do método de quadratura de Gauss-Hermite adaptativa como aproximação para as integrais dos efeitos aleatórios. Realiza-se um estudo de simulação para contrastar propriedades inferenciais do modelo aspirante com o modelo linear generalizado binomial, um modelo de quase-verossimilhança e o tradicional modelo linear generalizado hierárquico em dois níveis. / A common alternative when analyzing binary data originated from a two-level hierarchical structure (for instance, student and school) is to assume a binomial distribution for the experimental units of the first level (student) conditionally to a normal random effect for the second level units (school). In this work, we propose the inclusion of a second normal random effect in the first level to contemplate a possible extra-binomial variability due to the dependence among the Bernoulli trials in the same individual. We obtain the maximum likelihood estimation process for this hierarchical model starting from the marginal likelihood of the data, after a double application of the adaptive Gauss-Hermite quadrature as an approximation of the integrals of the random effects. We conduct a simulation study to compare the inferential properties of the advocated model with the generalized linear (binomial) model, a quasi-likelihood model and the usual two-level hierarchical generalized linear model.
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Modelling dependence in actuarial science, with emphasis on credibility theory and copulasPurcaru, Oana 19 August 2005 (has links)
One basic problem in statistical sciences is to understand the relationships among multivariate outcomes. Although it remains an important tool and is widely applicable,
the regression analysis is limited by the basic setup that requires to identify one dimension of the outcomes as the primary measure of interest (the "dependent"
variable) and other dimensions as supporting this variable (the "explanatory" variables). There are situations where this relationship is not of primary interest.
For example, in actuarial sciences, one might be interested to see the dependence between annual claim numbers of a policyholder and its impact on the premium
or the dependence between the claim amounts and the expenses related to them. In such cases the normality hypothesis fails, thus Pearson's correlation or concepts based
on linearity are no longer the best ones to be used. Therefore, in order to quantify the dependence between non-normal outcomes one needs different statistical tools,
such as, for example, the dependence concepts and the copulas.
This thesis is devoted to modelling dependence with applications in actuarial sciences and is divided in two parts: the first one concerns dependence in frequency
credibility models and the second one dependence between continuous outcomes. In each part of the thesis we resort to different tools, the stochastic orderings
(which arise from the dependence concepts), and copulas, respectively.
During the last decade of the 20th century, the world of insurance was confronted with important developments of the a posteriori tarification, especially in the
field of credibility. This was dued to the easing of insurance markets in the European Union, which gave rise to an advanced segmentation. The first important
contribution is due to Dionne & Vanasse (1989), who proposed a credibility model which integrates a priori and a posteriori information on an individual basis.
These authors introduced a regression component in the Poisson counting model in order to use all available information in the estimation of accident frequency.
The unexplained heterogeneity was then modeled by the introduction of a latent variable representing the influence of hidden policy characteristics. The vast majority
of the papers appeared in the actuarial literature considered time-independent (or static) heterogeneous models. Noticeable exceptions include the pioneering papers
by Gerber & Jones (1975), Sundt (1988) and Pinquet, Guillén & Bolancé (2001, 2003). The allowance for an unknown underlying random parameter
that develops over time is justified since unobservable factors influencing the driving abilities are not constant. One might consider either shocks (induced by
events like divorces or nervous breakdown, for instance) or continuous modifications (e.g. due to learning effect).
In the first part we study the recently introduced models in the frequency credibility theory, which can be seen as models of time series
for count data, adapted to actuarial problems. More precisely we will examine the kind of dependence induced among annual claim numbers by the introduction of random
effects taking unexplained heterogeneity, when these random effects are static and time-dependent. We will also make precise the effect of reporting claims on the
a posteriori distribution of the random effect. This will be done by establishing some stochastic monotonicity property of the a posteriori distribution
with respect to the claims history. We end this part by considering different models for the random effects and computing the a posteriori corrections of the
premiums on basis of a real data set from a Spanish insurance company.
Whereas dependence concepts are very useful to describe the relationship between multivariate outcomes, in practice (think for instance to the computation of reinsurance
premiums) one need some statistical tool easy to implement, which incorporates the structure of the data. Such tool is the copula, which allows the construction of multivariate
distributions for given marginals. Because copulas characterize the dependence structure of random vectors once the effect of the marginals has been factored out,
identifying and fitting a copula to data is not an easy task. In practice, it is often preferable to restrict the search of an appropriate copula to some reasonable
family, like the archimedean one. Then, it is extremely useful to have simple graphical procedures to select the best fitting model among some competing alternatives
for the data at hand.
In the second part of the thesis we propose a new nonparametric estimator for the generator, that takes into account the particularity of the data, namely censoring and truncation.
This nonparametric estimation then serves as a benchmark to select an appropriate parametric archimedean copula. This selection procedure will be illustrated
on a real data set.
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Testing for spatial correlation and semiparametric spatial modeling of binary outcomes with application to aberrant crypt foci in colon carcinogenesis experimentsApanasovich, Tatiyana Vladimirovna 01 November 2005 (has links)
In an experiment to understand colon carcinogenesis, all animals were exposed to a carcinogen while half the animals were also exposed to radiation. Spatially, we measured the existence of aberrant crypt foci (ACF), namely morphologically changed colonic crypts that are known to be precursors of colon cancer development. The biological question of interest is whether the locations of these ACFs are spatially correlated: if so, this indicates that damage to the colon due to carcinogens and radiation is localized. Statistically, the data take the form of binary outcomes (corresponding to the existence of an ACF) on a regular grid. We develop score??type methods based upon the Matern and conditionally autoregression (CAR) correlation models to test for the spatial correlation in such data, while allowing for nonstationarity. Because of a technical peculiarity of the score??type test, we also develop robust versions of the method. The methods are compared to a generalization of Moran??s test for continuous outcomes, and are shown via simulation to have the potential for increased power. When applied to our data, the methods indicate the existence of spatial correlation, and hence indicate localization of damage. Assuming that there are correlations in the locations of the ACF, the questions are how great are these correlations, and whether the correlation structures di?er when an animal is exposed to radiation. To understand the extent of the correlation, we cast the problem as a spatial binary regression, where binary responses arise from an underlying Gaussian latent process. We model these marginal probabilities of ACF semiparametrically, using ?xed-knot penalized regression splines and single-index models. We ?t the models using pairwise pseudolikelihood methods. Assuming that the underlying latent process is strongly mixing, known to be the case for many Gaussian processes, we prove asymptotic normality of the methods. The penalized regression splines have penalty parameters that must converge to zero asymptotically: we derive rates for these parameters that do and do not lead to an asymptotic bias, and we derive the optimal rate of convergence for them. Finally, we apply the methods to the data from our experiment.
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Testing for spatial correlation and semiparametric spatial modeling of binary outcomes with application to aberrant crypt foci in colon carcinogenesis experimentsApanasovich, Tatiyana Vladimirovna 01 November 2005 (has links)
In an experiment to understand colon carcinogenesis, all animals were exposed to a carcinogen while half the animals were also exposed to radiation. Spatially, we measured the existence of aberrant crypt foci (ACF), namely morphologically changed colonic crypts that are known to be precursors of colon cancer development. The biological question of interest is whether the locations of these ACFs are spatially correlated: if so, this indicates that damage to the colon due to carcinogens and radiation is localized. Statistically, the data take the form of binary outcomes (corresponding to the existence of an ACF) on a regular grid. We develop score??type methods based upon the Matern and conditionally autoregression (CAR) correlation models to test for the spatial correlation in such data, while allowing for nonstationarity. Because of a technical peculiarity of the score??type test, we also develop robust versions of the method. The methods are compared to a generalization of Moran??s test for continuous outcomes, and are shown via simulation to have the potential for increased power. When applied to our data, the methods indicate the existence of spatial correlation, and hence indicate localization of damage. Assuming that there are correlations in the locations of the ACF, the questions are how great are these correlations, and whether the correlation structures di?er when an animal is exposed to radiation. To understand the extent of the correlation, we cast the problem as a spatial binary regression, where binary responses arise from an underlying Gaussian latent process. We model these marginal probabilities of ACF semiparametrically, using ?xed-knot penalized regression splines and single-index models. We ?t the models using pairwise pseudolikelihood methods. Assuming that the underlying latent process is strongly mixing, known to be the case for many Gaussian processes, we prove asymptotic normality of the methods. The penalized regression splines have penalty parameters that must converge to zero asymptotically: we derive rates for these parameters that do and do not lead to an asymptotic bias, and we derive the optimal rate of convergence for them. Finally, we apply the methods to the data from our experiment.
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Modelos lineares generalizados mistos para dados longitudinais. / Generalized linear mixed models in longitudinal data.Silvano Cesar da Costa 13 March 2003 (has links)
Experimentos cujas variaveis respostas s~ ao proporcoes ou contagens, sao muito comuns nas diversas areas do conhecimento, principalmente na area agricola. Na analise desses experimentos, utiliza-se a teoria de modelos lineares generalizados, bastante difundida (McCullagh & Nelder, 1989; Demetrio, 2001), em que as respostas sao independentes. Caso a variancia estimada seja maior do que a esperada, estima-se o parametro de dispersao, incluindo-o no processo de estimaçao dos parametros. Quando a variavel resposta e observada ao longo do tempo, pode haver uma correlacao entre as observacoes e isso tem que ser levado em consideracao na estimacao dos parametros. Uma forma de se trabalhar essa correlacao e aplicando a metodologia de equacoes de estimacao generalizada (EEG), discutida por Liang & Zeger (1986), embora, neste caso, o interesse esteja nas estimativas dos efeitos fixos e a inclusao da matriz de correlacao de trabalho sirva para se obter um melhor ajuste. Uma outra alternativa e a inclusao, no preditor linear, de um efeito latente para captar variabilidades nao consideradas no modelo e que podem in uenciar nos resultados. No presente trabalho, usa-se uma forma combinada de efeito aleatorio e parametro de dispersao, incluidos conjuntamente na estimacao dos parametros. Essa metodologia e aplicada a um conjunto de dados obtidos de um experimento com camu-camu, com objetivo de se avaliarem quais os melhores metodos de enxertia e tipos de porta-enxertos que podem ser utilizados, atraves da proporcao de pegamentos da muda. Varios modelos sao ajustados, desde o modelo em parcelas subdivididas (supondo independencia), ate o modelo em que se considera o parametro de dispersao e efeito aleatorio conjuntamente. Ha evidencias de que o modelo em que se inclui o efeito aleatorio e o parametro de dispersao, conjuntamente, resultam em melhores estimativas dos parametros. Outro conjunto de dados longitudinais, com milho transgenico MON810, em que a variavel resposta e o numero de lagartas (Spodoptera frugiperda), e utilizado. Neste caso, devido ao excesso de respostas zero, emprega-se o modelo de regressao Poisson in acionado de zeros (ZIP), alem do modelo Poisson padrao, em que as observacoes sao consideradas independentes, e do modelo Poisson in acionado de zeros com efeito aleatorio. Os resultados mostram que o efeito aleatorio incluido no preditor foi nao significativo e, assim, o modelo adotado e o modelo de regressao Poisson in acionado de zeros. Os resultados foram obtidos usando-se os procedimentos NLMIXED, GENMOD e GPLOT do SAS - Statistical Analysis System, versao 8.2. / Experiments which response variables are proportions or counts are very common in several research areas, specially in the area of agriculture. The theory of generalized linear models, well difused (McCullagh & Nelder, 1989; Demetrio, 2001), is used for analyzing these experiments where the responses are independent. If the estimated variance is greater than the expected variance, the dispersion parameter is estimated including it on the parameter estimation process. When the response variable is observed over time a correlation among observations might occur and it should be taken into account in the parameter estimation. A way of dealing with this correlation is applying the methodology of generalized estimating equations (GEEs) discussed by Liang & Zeger (1986) although, in this case, the interest is on the estimates of the xed efect being the inclusion of a working correlation matrix useful to obtain more accurate estimates. Another alternative is the inclusion of a latent efect in the linear predictor to explain variabilities not considered in the model that might in uence the results. In this work the random efect and the dispersion parameter are combined and included together in the parameter estimation. Such methodology is applied to a data set obtained from an experiment realized with camu-camu to evaluate, through proportion of grafting well successful of seedling, which kind of grafting and understock are suitable to be used. Several models are fitted, since the split plot model (with independence assumption) up to the model where the dispersion parameter and the random efect are considered together. There is evidence that the model including the random efect and the dispersion parameter together, produce better estimates of the parameters. Another longitudinal data set used here comes from an experiment realized with the MON810 transgenic corn where the response variable is the number of caterpillars (Spodoptera frugiperda). In this case, due to the excessive number of zeros obtained, the zero in ated Poisson regression model (ZIP) is used in addition to the standard Poisson model, where observations are considered independent, and the zero in ated Poisson regression model with random efect. The results show that the random efect included in the linear predictor was not significant and, therefore, the adopted model is the zero in ated Poisson regression model. The results were obtained using the procedures NLMIXED, GENMOD and GPLOT available on SAS - Statistical Analysis System, version 8.2.
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Estimativa do custo da colheita mecanizada de cana-de-açúcar utilizando modelos de regressão / Estimated cost of mechanized harvesting of sugarcane using regression modelsEduardo Shigueiti Maekawa 22 August 2016 (has links)
A colheita mecanizada é uma das mais significativas e onerosas operações do processo de produção de cana-de-açúcar, tornando-se importante o entendimento das relações que envolvem o seu custo. Atualmente, as metodologias para estimar o custo da colheita partem do conceito de custo fixo e variável. No entanto, considerando a complexidade desse processo, faz-se necessário avaliar métodos capazes de relacionar os parâmetros operacionais com o custo final. Neste contexto, a modelagem estatística por meio da regressão permite tratar tais relações e prever tendências. O objetivo deste trabalho foi desenvolver um modelo empírico para o cálculo do custo da colheita mecanizada de cana-de-açúcar. Desenvolveu-se um modelo linear generalizado (MLG) e um modelo linear generalizado misto (MLGM) ambos com distribuição gama, utilizando indicadores operacionais e dados de custo de 20 usinas do setor sucroalcooleiro. Por meio do MLGM, obteve-se uma aderência satisfatória quando comparado aos modelos MLG, nulo (média) e linear (supondo normalidade). Os indicadores que explicaram o custo foram: produtividade (t maq-1), consumo (l t-1), horímetro (h) e número de operadores por colhedora (nop). / The mechanized harvesting of sugarcane is one of the most significant and costly operations of the production process, thus it is important to understand the relationships involving its cost. Currently, methods to estimate these costs rise from the concept of fixed and variable cost. However, considering the complexity of the harvesting process, it is necessary to evaluate techniques to relate the operating parameters with the final cost. In this context, statistical modeling by regression allows to treat such relationship and predict trends. The objective of this study was to develop an empirical model to calculate the cost of mechanical harvesting of sugarcane. A generalized linear model (GLM) and a generalized linear mixed model (GLMM) both with gamma distribution was developed using operational indicators and cost data from 20 plants in the sugarcane industry. Through the GLMM, satisfactory adhesion was obtained when compared to the GLM, null model (average) and linear (assuming normality). The indicators that explained the cost were: productivity (t mach-1), consumption (l t-1), hourmeter (h) and number of operators per harvester (nop).
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Modelos estatísticos para dados politômicos nominais em estudos longitudinais com uma aplicação à área agronômica / Statistical models for nominal polytomous data in longitudinal studies with an application to agronomyVinicius Menarin 14 January 2016 (has links)
Estudos em que a resposta de interesse é uma variável categorizada são bastante comuns nas mais diversas áreas da Ciência. Em muitas situações essa resposta é composta por mais de duas categorias não ordenadas, denominada então de uma variável politômica nominal, e em geral o objetivo do estudo é associar a probabilidade de ocorrência de cada categoria aos efeitos de variáveis explicativas. Ademais, existem tipos especiais de estudos em que os dados são coletados diversas vezes para uma mesma unidade amostral ao longo do tempo, os estudos longitudinais. Estudos assim requerem o uso de modelos estatísticos que considerem em sua formulação algum tipo de estrutura que suporte a dependência que tende a surgir entre observações feitas em uma mesma unidade amostral. Neste trabalho são abordadas duas extensões do modelo de logitos generalizados, usualmente empregado quando a resposta é politômica nominal com observações independentes entre si. A primeira consiste de uma modificação das equações de estimação generalizadas para dados nominais que se utiliza de razões de chances locais para descrever a dependência entre as observações da variável resposta politômica ao longo dos diversos tempos observados. Este tipo de modelo é denominado de modelo marginal. A segunda proposta abordada consiste no modelo de logitos generalizados com a inclusão de efeitos aleatórios no preditor linear, que também leva em conta uma dependência entre as observações. Esta abordagem caracteriza o modelo de logitos generalizados misto. Há diferenças importantes inerentes às interpretações dos modelos marginais e mistos, que são discutidas e que devem ser levadas em consideração na escolha da abordagem adequada. Ambas as propostas são aplicadas em um conjunto de dados proveniente de um experimento da área agronômica realizado em campo, conduzido sob um delineamento casualizado em blocos com esquema fatorial para os tratamentos. O experimento foi acompanhado ao longo de seis estações do ano, caracterizando assim uma estrutura longitudinal, sendo a variável resposta o tipo de vegetação observado no campo (touceiras, plantas invasoras ou espaços vazios). Os resultados encontrados são satisfatórios, embora a dependência presente nos dados não seja tão caracterizada; por meio de testes como da razão de verossimilhanças e de Wald diversas diferenças significativas entre os tratamentos foram encontradas. Ainda, devido às diferenças metodológicas das duas abordagens, o modelo marginal baseado nas equações de estimação generalizadas mostra-se mais adequado para esses dados. / Studies where the response is a categorical variable are quite common in many fields of Sciences. In many situations this response is composed by more than two unordered categories characterizing a nominal polytomous outcome and, in general, the aim of the study is to associate the probability of occurrence of each category to the effects of variables. Furthermore, there are special types of study where many measurements are taken over the time for the same sampling unit, called longitudinal studies. Such studies require special statistical models that consider some kind of structure that support the dependence that tends to arise from the repeated measurements for the same sampling unit. This work focuses on two extensions of the baseline-category logit model usually employed in cases when there is a nominal polytomous response with independent observations. The first one consists in a modification of the well-known generalized estimating equations for longitudinal data based on local odds ratios to describe the dependence between the levels of the response over the repeated measurements. This type of model is also known as a marginal model. The second approach adds random effects to the linear predictor of the baseline-category logit model, which also considers a dependence between the observations. This characterizes a baseline-category mixed model. There are substantial differences inherent to interpretations when marginal and mixed models are compared, what should be considered in the choice of the most appropriated approach for each situation. Both methodologies are applied to the data of an agronomic experiment installed under a complete randomized block design with a factorial arrangement for the treatments. It was carried out over six seasons, characterizing the longitudinal structure, and the response is the type of vegetation observed in field (tussocks, weeds or regions with bare ground). The results are satisfactory, even if the dependence found in data is not so strong, and likelihood-ratio and Wald tests point to several differences between treatments. Moreover, due to methodological differences between the two approaches, the marginal model based on generalized estimating equations seems to be more appropriate for this data.
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Ecology and diet of the caracal (Caracal caracal) on lethal and non-lethal control farms in the KarooJooste, Erin Cecilia January 2020 (has links)
>Magister Scientiae - MSc / Human-wildlife conflict is an ongoing issue worldwide. Within South Africa, human-carnivore conflict (HCC) as a result of carnivore depredation on small-livestock causes large-scale losses, and promotes the use of predator management tools by farmers. Despite being one of the major offenders involved in HCC, caracals, and their ecology in particular, are understudied. This is mainly due to high levels of persecution, coupled with their elusive nature. Within the Karoo region of South Africa, pastoralists make use of large-scale lethal predator controls in an attempt to remove the offenders, or non-lethal predator controls to protect livestock and deter predators. However, the effects of these various predator control techniques on caracal ecology have not been widely tested. Therefore, the aims of this thesis were, firstly, to assess caracal diet on lethal and non-lethal treatment farms in the Karoo; secondly, to investigate the drivers of caracal habitat selection on a non-lethal farm in the Karoo; and finally, to evaluate caracal activity patterns on the non-lethal farm. To do this, I made use of two non-invasive techniques (i.e. scat analysis and camera trapping). Caracals appeared to favour natural prey across all sites, with livestock remains only found in scats collected at the lethal treatment farm. Caracals had the broadest dietary breadth on the non-lethal treatment site, and the narrowest on the lethal treatment site. The main components of caracal diet included small mammals, lagomorphs, rock hyraxes (Procavia capensis), wild ungulates and arthropods. Caracal habitat selection was explained by resource dispersion and environmental features Interestingly, the presence of livestock was not a major consideration in caracal habitat selection. Caracals were mainly nocturnal but became increasingly crepuscular during winter. In addition, caracal activity overlapped significantly with black-backed jackals (Canis mesomelas), lagomorphs and common duikers (Sylvicapra grimmia). Caracals showed plasticity in their activity patterns based on seasonal temperature fluctuations, and partially human avoidance. This study contributes to understanding how caracal ecology differs on differently managed livestock farms. Throughout this study, the importance of both a natural prey base, as well as natural lands to caracal survival have been revealed. These findings can contribute to caracal conservation in HCC areas.
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Modelos lineares mistos e generalizados mistos em estudos de adaptação local e plasticidade fenotípica de Euterpe edulis / Linear mixed models and generalized mixed models applied in studies of local adaptation and phenotypic plasticity of Euterpe edulisBautista, Ezequiel Abraham López 18 June 2014 (has links)
Este trabalho objetivou a avaliação da presença de plasticidade fenotípica e de adaptação local de três procedências de palmiteiro: Ombrófila Densa, Estacional Semidecidual e Restinga, em três locais no Estado de São Paulo: Parque Estadual da Ilha do Cardoso, Parque Estadual de Carlos Botelho e Estação Ecológica dos Caetetus, em ensaios de adaptação no estabelecimento (ou de semeadura) e de adaptação em juvenis (ou de crescimento). Os conjuntos de dados foram analisados utilizando estruturas de grupos de experimentos, com efeitos cruzados e aninhados. As variáveis relacionadas com a massa de matéria seca das plantas, nos dois ensaios, foram analisadas usando a abordagem de modelos lineares de efeitos mistos, por meio da incorporação de fatores de efeito aleatório, e fazendo uso do método da máxima verossimilhança restrita (REML) para estimação dos componentes de variância associados a tais fatores com um menor viés. Por outro lado, para a proporção de sementes germinadas, no ensaio de adaptação no estabelecimento, a análise estatística foi realizada a partir da abordagem dos modelos lineares generalizados mistos, sob a pressuposição de que a variável segue uma distribuição binomial, com função de ligação logito. O método da pseudo-verossimilhança foi empregado para obtenção da solução das equações de verossimilhança. Os resultados mostraram que as plantas originadas de sementes dos três biomas avaliados apresentaram um comportamento plástico, para todos os caracteres avaliados no ensaio de adaptação no estabelecimento. Com relação ao ensaio de adaptação em juvenis, a característica de plasticidade foi verificada somente para a massa de matéria seca da folha em plantas provenientes do bioma Estacional Semidecidual. A característica de adaptação local, apresentou-se de forma evidente no ensaio de adaptação no estabelecimento. Estes resultados evidenciaram que em cada local avaliado, as plantas originadas das sementes de diferentes procedências apresentaram um comportamento diferenciado nos caracteres relacionados à massa de matéria seca, podendo em alguns casos, tratar-se de adaptação local. Concluiu-se que os locais Carlos Botelho e Ilha do Cardoso são os mais favoráveis para a germinação das sementes de sua mesma procedência. / The aim of this work was to evaluate the presence of phenotypic plasticity and local adaptation of three provenances of the palm specie Euterpe edulis: Atlantic Rainforest, Seasonally Dry Forest and Restinga Forest, in permanent parcels inserted in three forest types of the São Paulo State (Brazil): Parque Estadual da Ilha do Cardoso, Parque Estadual de Carlos Botelho e Estação Ecológica dos Caetetus, in experiments of seedling establishment and juveniles plants growth. The data sets were analyzed using structures of groups of experiments, with crossed and nested effects. The variables related to dry matter content of plants in both assays were analyzed using linear mixed models (LMM) approach, through the incorporation of random effect factors, and using the restricted maximum likelihood method (REML) for estimation of variance components associated with these factors with a minor bias. On the other hand, germination proportion of the seeds at seedling establishment assay was analyzed using the generalized linear mixed models (GLMM) approach, under the assumption that the variable follows a binomial distribution, with logit link function. The pseudo-likelihood (PL) method was used to obtain the numerical solution of the likelihood equations. The results showed that, plants from seeds of the three biomes evaluated presented a plastic behavior for all characters assessed in the seedling establishment assay. In respect to juveniles adaptation assay, the phenotypic plasticity characteristic was observed only to the leaf dry matter content of plants from Seasonally Dry Forest biome. The local adaptation characteristic was clearly observed in the seedling establishment assay. These results showed that at each site evaluated, plants originating from seeds of different provenances exhibited different behavior on characters related to the dry matter content and may in some cases be local adaptation. It was concluded that locations Carlos Botelho and Ilha do Cardoso are the most favorable for seed germination of its same provenance.
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