Thesis (Ph. D.)--Virginia Polytechnic Institute, 1963. / Vita. Abstract. Includes bibliographical references (leaves 124-126). Also available via the Internet.

Resumo: O estudo da distribuição espacial de pragas é fundamental para elaboração de planos de amostragem para uso no manejo integrado de pragas. Para Toxoptera citricida foi estudada a distribuição espacial em talhões de pomares de citros comerciais de laranja (Citrus sinensis) da variedade Pêra, com 5, 9 e 15 anos de idade, durante o período de setembro de 2004 a abril de 2005. Foram realizadas 14 amostragens de número de pulgões-preto em intervalos aproximados de 15 dias entre as mesmas, utilizando-se armadilhas adesivas de cor amarela (0,11 x 0,11 m) fixadas à planta a 1,5 m de altura aproximadamente. As armadilhas foram distribuídas na área, a cada cinco plantas na linha, em linhas alternadas, totalizando 137 armadilhas no talhão com 5 anos, 140 no talhão com 9 anos e 80 no talhão com 15 anos. A lei de Taylor e a distribuição binomial negativa foram os modelos que melhor representaram a distribuição da população. Foram com construídos planos de amostragens para levantamento desta praga com base na lei de Taylor e na distribuição binomial negativa. / Abstract: The study of spatial distribution of insects is fundamental to elaborate sampling plans with potential to use in integrated pest management. The spatial distribution of Toxoptera citricida was studied in plots of commercial orchards of orange (Citrus sinensis) of the variety 'Pêra' with 5, 9 and 15 years of age, during the period of September of 2004 and April of 2005. Fourteen samples of the number of Toxoptera citricida was performed each 15d approximately, using yellow adhesive traps fixed at 1,5 m of height each 5 plants in alternated lines, summing 137 traps in the 5-years plot, 140 traps in the 9-years plot and 80 traps in the 15-years plot. The best models fitted the distribution of population were the Taylor Law and negative binomial distribution, which were used to elaborate the sampling plans. / Orientador: José Carlos Barbosa / Coorientador: Pedro Takao Yamamoto / Banca: Antonio Carlos Busoli / Banca: Wilson Itamar Maruyama / Mestre

This thesis is an extension of the development of orthogonal statistics which can be used to investigate sampling properties of moment estimators. This work is particularized for estimators of parameters of the negative binomial distribution. / Master of Science

Ph. D.

Ph. D.

This dissertation deals primarily with the development of the technique of orthogonal statistics and the use of this technique to investigate sampling properties of moment estimators of parameters of the negative binomial distribution. The general technique of orthogonal statistics which is based on the existence of an infinite set {q_r(x)} of orthogonal polynomials associated with a particular distribution, enables one to obtain expansions of sampling moments of statistics which are functions of say, the first k sample moments m₁, m₂,…, m_k. The thesis describes the technique in general, and gives tables which facilitate the expansion through terms in n⁻⁵ of sampling moments of statistics which are functions of any four sample moments. The need for the development of this technique resulted from an interest in the problem of investigating sampling properties of certain moment estimators for the case of the negative binomial distribution. Thus further work was done on the technique for this particular case. Tables are given in the thesis which simplify the procedure for moment statistics which result from a sample taken from this particular distribution. Sampling properties of moment estimators for the negative binomial distribution were investigated. The distribution forms considered in depth were due to Anscombe [Biometrika, 37 (1950}, pp. 358-362] with parameters λ and α, Evans [Biometrika, 40 (1953), pp. 186-211] with parameters m and a, and Fisher [Annals of Eugenics, 11 (1941), pp. 182-187] with parameters p and k. The purpose of this study was to obtain an insight into the behavior of expansions through high powers of 1/n (e.g., terms in n⁻⁴) of the bias, variance, and higher moments for these estimators. It was felt that the usual asymptotic properties described by the first term approximations might be misleading for practical cases (i.e., ordinary sample sizes). The results verified what was suspected. For the moment estimators of Ansaombe's form, when α > λ the sample sizes needed to make high order terms negligible for the expansion of the bias and variance were extremely large. (For one particular case, in order to use the usual asymptotic variance safely one would need an n of 2 million.) This then reveals the hazardous practice of using the first term approximation and resulting in a very serious under-assessment of the true variance of the estimate of α. Since for Fisher's form k̂ = α̂, the same applies. For Evans' form, the situation was in marked contrast. Higher order terms were "damped off" with much smaller sample sizes, and in most cases one is justified in using first term approximations. Studies for Evans' estimators were confined to the range λ > 1 and α > 1. The results for the estimators of Anscombe's form were compared with similar results for the maximum likelihood estimator of α, in order to ascertain the effect on efficiency of the chaotic nature of the n⁻³ term in the expansion of the covariance determinant of α̂. The maximum likelihood results were taken from Bowman [Thesis submitted for Ph.D. degree, Virginia Polytechnic Institute, Moments to Higher Orders for Maximum Likelihood Estimators with an Application to the Negative Binomial Distribution]. This study revealed that there is a striking similarity in the n⁻³ term in the covariance determinant for the two estimators. This made the "true" efficiency almost identical to the asymptotic efficiency in cases when sufficiently large sample sizes are used to "sink" terms beyond n⁻³. This statement cannot be generalized, however, to include any sample size, since for α > λ only relatively large sample sizes "damp off' further terms in the covariance determinants for both estimators. Hence one cannot be sure of the behavior of these determinants beyond n⁻³ unless these large sample sizes are used. Tables and charts are given which display the nature of the expansions given in the text. In particular, charts are given of minimum sample size needed in order that the expansions given can safely be used as approximations. / Ph. D.

This dissertation deals with the properties of two modified moment estimators for parameters of the negative binomial distribution (NBD). Several parametric forms have been suggested for the NBD. The estimation problems vary according to the form which is used. In particular, the form proposed by Anscombe [Biometrika, 37 (1950), pp. 358-382), with parameters λ and α, has received wide attention and was selected for study in this investigation. In Anscombe's parametric form, the mean of the NBD is λ and the variance is λ + λ²/α. While the parameter λ is universally estimated by the sample mean, many different methods of estimation for α have been attempted. Among these, the maximum likelihood estimator α* and the simple moment estimator â are most often used. However, α* is quite difficult to obtain numerically and often this computation requires the use of an electronic computer. In addition, â, while not difficult to compute, is often inefficient. For these reasons, it was felt that a study of the two modified moment estimators â₁ and â₂, suggested by Shenton and Wallington [Moment Estimators and Modified Moment Estimators with Special Reference to the Negative Binomial Distribution (unpublished)], was needed. In the text, the method of obtaining modified moment estimators in general is given in detail. The application of this method to the NBD is discussed and, in particular, the derivations of â₁ and â₂ are presented. Since orthogonal statistics play an important part in this work, their definition and applications are reviewed. In order to evaluate the small sample properties of â₁ and â₂, asymptotic expansions, in powers of 1/n, of their biases, variances, covariance determinants, and higher moments were determined numerically in the parameter space (1 ≤ α ≤ 100, 1 ≤ λ ≤ 100), through terms to n⁻⁴. The computational method for this work is described in detail. Tables and charts which display the nature of the expansions are given in the text. The results show that the behavior patterns of the moment expansions for â₁ and â₂ are somewhat similar to those for â and α*. For both â₁ and â₂, the n⁻⁴ term contributes heavily in all the expansions when α > λ. Thus, as with the other estimators, a first term approximation would not suffice for the properties of â₁ and â₂. Further, the results give evidence that â₁ and â₂ are highly efficient for most α and λ, and, in some regions of the parameter space, have less bias than α* and â. Some experimental data was fitted to the NBD using the estimators â₁, â₂, â, and α*. In all of the examples given, the modified moment estimators provided a better fit of the data than did the simple moment estimator and, in one instance, a better fit than was obtained by the maximum likelihood estimator. / Ph. D.

Thesis (M. Sc.)--Carleton University, 2008. / Includes bibliographical references (p. 57-62). Also available in electronic format on the Internet.

Resumo: O psilídeo Diaphorina citri Kuwayama tornou-se nos últimos anos, uma das mais importantes pragas na cultura de citros, principalmente pelos prejuízos causados às plantas devido à transmissão da bactéria causadora da doença Huanglongbing (HLB) ou Greening. Com a finalidade de estudar a distribuição espacial de ninfas e adultos desta praga, instalou-se um experimento em 2 áreas de citros com histórico de ocorrência de HLB, no município de Matão, região central do Estado de São Paulo, uma com plantas de 4 anos e outra com plantas de 12 anos de idade. Para estudo da agregação da população nas plantas, foram utilizados os seguintes índices de dispersão: razão variância/média (I), índice de Morisita (Id), coeficiente de Green (Cx) e expoente k da distribuição binomial negativa para cada amostragem. A distribuição binomial negativa foi o modelo mais adequado para representar a distribuição espacial do psilídeo na cultura de citros, tanto para ninfas como para adultos. Através da análise destes índices, verificou-se que, na maioria das amostragens, as ninfas encontradas nas brotações e os adultos capturados nas armadilhas apresentaram distribuição agregada. Foram desenvolvidos planos de amostragem seqüencial para ninfas e adultos em região com e sem HLB, e os números máximos de amostras esperados para se tomar a decisão foram de 264 e 83 para ninfas, em regiões com e sem a doença, e de 184 e 150 amostras para adultos, em regiões com e sem a doença. / Abstract: The psyllid Diaphorina citri Kuwayama is one of the most important pests of citrus, mostly because of plant damage due to transmission of the bacterium that causes Huanglongbing (HLB) or Greening disease. The experiment was carried out in 2 sweet orange orchards with previous HLB occurrence in Matão (central region of the State of São Paulo, Brazil), in plants with 4 and 12 years of age, in order to study the spatial distribution of nymphs and adults of this pest. The following dispersion indices were used to study pest aggregation in the citrus plants: variance/mean relationship (I), index of Morisita (Id), coefficient of Green (Cx), and the k exponent of negative binomial distribution for each sampling. The negative binomial distribution was the most representative spatial distribution of this psyllid in citrus, for both nymphs and adults. The analysis of these indices showed that, for most samplings, psyllid nymphs found in branches and adults caught in traps presented an aggregated distribution. Sequential sampling plans were developed for nymphs and adults in regions with and without HLB, and the maximum number of samples for decision making was 264 and 83 samples for nymphs in regions with and without the disease, and, 184 and 150 samples for adults, in regions with and without the disease, respectively. / Orientador: José Carlos Barbosa / Coorientador: Pedro Takao Yamamoto / Banca: Odair Aparecido Fernandes / Banca: Wilson Itamar Maruyama / Banca: Antonio Baldo Geraldo Martins / Banca: Eduardo Sanches Stuchi / Doutor

Made available in DSpace on 2014-06-11T19:28:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-06-05Bitstream added on 2014-06-13T20:37:32Z : No. of bitstreams: 1 toledo_fr_me_jabo.pdf: 503818 bytes, checksum: 0c25df81cfee4dc01b57b77e3a7b22a0 (MD5) / Fundecitrus / O estudo da distribuição espacial de pragas é fundamental para elaboração de planos de amostragem para uso no manejo integrado de pragas. Para Toxoptera citricida foi estudada a distribuição espacial em talhões de pomares de citros comerciais de laranja (Citrus sinensis) da variedade Pêra, com 5, 9 e 15 anos de idade, durante o período de setembro de 2004 a abril de 2005. Foram realizadas 14 amostragens de número de pulgões-preto em intervalos aproximados de 15 dias entre as mesmas, utilizando-se armadilhas adesivas de cor amarela (0,11 x 0,11 m) fixadas à planta a 1,5 m de altura aproximadamente. As armadilhas foram distribuídas na área, a cada cinco plantas na linha, em linhas alternadas, totalizando 137 armadilhas no talhão com 5 anos, 140 no talhão com 9 anos e 80 no talhão com 15 anos. A lei de Taylor e a distribuição binomial negativa foram os modelos que melhor representaram a distribuição da população. Foram com construídos planos de amostragens para levantamento desta praga com base na lei de Taylor e na distribuição binomial negativa. / The study of spatial distribution of insects is fundamental to elaborate sampling plans with potential to use in integrated pest management. The spatial distribution of Toxoptera citricida was studied in plots of commercial orchards of orange (Citrus sinensis) of the variety 'Pêra' with 5, 9 and 15 years of age, during the period of September of 2004 and April of 2005. Fourteen samples of the number of Toxoptera citricida was performed each 15d approximately, using yellow adhesive traps fixed at 1,5 m of height each 5 plants in alternated lines, summing 137 traps in the 5-years plot, 140 traps in the 9-years plot and 80 traps in the 15-years plot. The best models fitted the distribution of population were the Taylor Law and negative binomial distribution, which were used to elaborate the sampling plans.