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STATISTICAL TEST FOR GENOTYPE AND ENVIRONMENT CONTRIBUTION IN THE GENOTYPES x ENVIRONMENTS INTERACTION MATRIX

Araujo, Mirian Fernandes Carvalho; Araujo, Lucio Borges de; Faria, Priscila Neves; Dias, Carlos Tadeu dos Santos
Fonte: INTERCIENCIA; CARACAS Publicador: INTERCIENCIA; CARACAS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.98%
The objective of the present work was to propose a method for testing the contribution of each level of the factors in a genotypes x environments (GxE) interaction using multi-environment trials analyses by means of an F test. The study evaluated a data set, with twenty genotypes and thirty-four environments, in a block design with four replications. The sum of squares within rows (genotypes) and columns (environments) of the GxE matrix was simulated, generating 10000 experiments to verify the empirical distribution. Results indicate a noncentral chi-square distribution for rows and columns of the GxE interaction matrix, which was also verified by the Kolmogorov-Smirnov test and Q-Q plot. Application of the F test identified the genotypes and environments that contributed the most to the GxE interaction. In this way, geneticists can select good genotypes in their studies.; Conselho Nacional Cientifico e Tecnologico (CNPq); Brazilian science funding agencies; Brazilian science funding agencies; CNPq

Redução no vício da distribuição da deviance para dados de contagem.; Bias reduction in the distribution of the deviance for count data.

Viola, Denise Nunes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/10/2001 PT
Relevância na Pesquisa
56.05%
Dados de contagem podem ser considerados, em geral, como provenientes de uma distribuição de Poisson. Neste contexto, a análise de tais dados apresenta certas dificuldades, pois não segue algumas pressuposições básicas para o ajuste de um modelo matemático. Desse modo, algumas transformações são sugeridas, mas nem sempre bons resultados são obtidos. No enfoque de Modelos Lineares Generalizados, a estatística que mede a qualidade do ajuste do modelo para os dados é chamada deviance. Porém, a distribuição da deviance é, em geral, desconhecida. No entanto, para dados com distribuição de Poisson, pode-se mostrar que a distribuição da deviance se aproxima de uma distribuição ?2, mas tal aproximação não é boa para tamanhos pequenos de amostra. Para melhorar essa aproximação, alguns fatores de correção para os dados são sugeridos, mas os resultados obtidos ainda não são satisfatórios. Assim, o objetivo deste trabalho é propor um novo fator de correção para os dados seguindo uma distribuição de Poisson, de modo a se obter uma melhora na distribuição da deviance para qualquer tamanho de amostra. Para isto, será adicionada uma constante à variável resposta e, através do valor esperado da deviance...

An adaptive chart for monitoring the process mean and variance

Costa, Antonio F. B.; De Magalhaes, Maysa S.
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 821-831
ENG
Relevância na Pesquisa
55.88%
Traditionally, an (X) over bar chart is used to control the process mean and an R chart is used to control the process variance. However, these charts are not sensitive to small changes in the process parameters. The adaptive ($) over bar and R charts might be considered if the aim is to detect small disturbances. Due to the statistical character of the joint (X) over bar and R charts with fixed or adaptive parameters, they are not reliable in identifing the nature of the disturbance, whether it is one that shifts the process mean, increases the process variance, or leads to a combination of both effects. In practice, the speed with which the control charts detect process changes may be more important than their ability in identifying the nature of the change. Under these circumstances, it seems to be advantageous to consider a single chart, based on only one statistic, to simultaneously monitor the process mean and variance. In this paper, we propose the adaptive non-central chi-square statistic chart. This new chart is more effective than the adaptive (X) over bar and R charts in detecting disturbances that shift the process mean, increase the process variance, or lead to a combination of both effects. Copyright (c) 2006 John Wiley & Sons...

Influence of dental care for infants on caries prevalence: A comparative study

Melhado, Fabiola Lemos; Cunha, Robson Frederico; Nery, Rosangela Santos
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 120-123
ENG
Relevância na Pesquisa
56.05%
Purpose: The influence of early dental care on the prevalence of dental caries was determined in children ages 35 to 40 months divided into 2 groups of 160 children each, with 1 group participating in a dental care program from the first year of life to the time of the study, while the other group did not receive any dental care. Methods: The clinical conditions considered for the evaluation were: sound teeth, enamel caries without cavitation, enamel caries with cavitation, and dentinal caries. The proportion and chi-square tests were used for statistical analysis with the level of significance set at 5%. Results: A significant difference regarding the presence of dental caries, especially in the number of children presenting enamel caries with cavitation (P<.0001), was observed between the 2 groups. The number of children with enamel caries without cavitation and dentinal caries was similar for the 2 groups. Conclusions: Considering the aspect of dental caries prevention, the authors concluded that children in the age range of 3 to 4 years who received early dental care showed better oral conditions.

The no-central chi-square chart with two-stage samplings

Costa, Antonio F.B.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 9
ENG
Relevância na Pesquisa
76.22%
Throughout this article, it is assumed that the no-central chi-square chart with two stage samplings (TSS Chisquare chart) is employed to monitor a process where the observations from the quality characteristic of interest X are independent and identically normally distributed with mean μ and variance σ2. The process is considered to start with the mean and the variance on target (μ = μ0; σ2 = σ0 2), but at some random time in the future an assignable cause shifts the mean from μ0 to μ1 = μ0 ± δσ0, δ >0 and/or increases the variance from σ0 2 to σ1 2 = γ2σ0 2, γ > 1. Before the assignable cause occurrence, the process is considered to be in a state of statistical control (defined by the in-control state). Similar to the Shewhart charts, samples of size n 0+ 1 are taken from the process at regular time intervals. The samplings are performed in two stages. At the first stage, the first item of the i-th sample is inspected. If its X value, say Xil, is close to the target value (|Xil-μ0|< w0σ 0, w0>0), then the sampling is interrupted. Otherwise, at the second stage, the remaining n0 items are inspected and the following statistic is computed. Wt = Σj=2n 0+1(Xij - μ0 + ξiσ 0)2 i = 1,2 Let d be a positive constant then ξ...

Divine proportions and facial esthetics after manipulation of frontal photographs.

Medici Filho, Edmundo; Martins, Márcia Valéria; dos Santos da Silva, Marcos André; Castilho, Julio Cezar de Melo; de Moraes, Luiz Cesar; Gil, Cássia Teresinha Lopes de Alcântara
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 103-108
ENG
Relevância na Pesquisa
56.05%
AIM: To investigate the relationship between divine proportion and facial esthetics in frontal photographs as well as whether any of the 4 ratios for manipulation provide more favorable facial esthetics. MATERIAL AND METHODS: The sample comprised 20 frontal photographs of Caucasian individuals (11 males and 9 females). The photographs were digitized and stored on a compact disk. A photometric analysis was created with 7 facial segments that were measured on Image Tool software and 4 ratios between 2 facial segments calculated using Microsoft Excel. This manipulation led to 5 different photographs of the same individual: one photograph with no manipulation and the others with 1 of the ratios manipulated in the Deformer 2.0 to very close or equal to 1.618. Thereafter, the 5 photographs of all individuals were evaluated by 12 examiners. The examiners selected those photographs that were esthetically more pleasant. CONCLUSION: After evaluation, a chi-square test revealed a relationship between divine proportion and facial esthetics. Among the ratios selected, R1 and R2 provided more favorable facial esthetics.

Influence of TNF-α blockers on the oral prevalence of opportunistic microorganisms in ankylosing spondylitis patients

Pereira, D. F A; Pinheiro, M. M.; Silva, P. N F; Teodoro, G. R.; Brighenti, F. L.; Koga-Ito, C. Y.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 679-685
ENG
Relevância na Pesquisa
55.88%
Objectives: To compare the oral prevalence and antimicrobial susceptibility of Candida spp., staphylococci, enterobacteriaceae, and pseudomonas spp.from ankylosing spondylitis (AS) patients receiving conventional and anti-TNF-α therapy. Methods: The study included 70 AS patients, diagnosed according to the modified New York criteria (1984). The volunteers were divided into 2 groups: a biological group (AS BioG) (n=35) (on anti-TNF-α therapy) and a conventional group (AS ConvG) (n=35). The control group (ContG) (n=70) was made up of healthy individuals matched for age, gender, and oral conditions. After clinical examination, oral rinse samples were collected and plated in specific culture media. The number of colony-forming units per milliliter (cfu/ml) was obtained, and isolates were identified using the API system. Antimicrobial susceptibility tests were performed according to the NCCLS guidelines. Prevalence and counts of microorganisms were statistically compared between the 3 groups, using the Mann-Whitney and Chi-square tests. Significance level was set at 5%. Results: In both the AS BioG and the AS ConvG, staphylococci counts were higher than that in the ContG (p<0.0001). Candida albicans and staphylococcus epidermidis were the most commonly found species in all the groups. Serratia marcescens and klebsiella oxytoca were more prevalent in the AS BioG and the AS ConvG...

Speed and Accuracy Comparison of Noncentral Chi-Square Distribution Methods for Option Pricing and Hedging under the CEV Model

Larguinho, M.; Dias, J.C.; Braumann, C.A.
Fonte: Em: Conference Proceedings of 18th International Conference on Forecasting Financial Markets: Advances for Exchange Rates, Interest Rates and Asset Management (CD-ROM) Publicador: Em: Conference Proceedings of 18th International Conference on Forecasting Financial Markets: Advances for Exchange Rates, Interest Rates and Asset Management (CD-ROM)
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
96.08%
Pricing options and evaluating greeks under the constant elasticity of variance (CEV) model require the computation of the noncentral chi-square distribution function. In this article, we compare the performance in terms of accuracy and computational time of alternative methods for computing such probability distributions against an xternally tested benchmark. In addition, we present closed-form solutions for computing greek measures under the CEV option pricing model for both beta < 2 and beta > 2, thus being able to accommodate direct leverage effects as well as inverse leverage effects that are frequently observed in the options markets.

Detection of inbreeding effects by the chi-square test on genotypic and phenotypic frequencies.

Haber, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1980 EN
Relevância na Pesquisa
55.98%
The problem of detection of inbreeding effects by the chi-square goodness-of-fit test is investigated. The noncentrality parameter of the limiting chi-square distribution is considered as a function of the inbreeding coefficient in two models: (1) a gene locus with m codominant alleles and (2) the generalized ABO model. Previous results by Ward and Sing and by Chakraborty and Rao were based on inadequate statistical reasoning. In the first model, the resulting noncentrality parameter is identical with that found by Ward and Sing. For the second model, the limiting noncentrality parameter is found to be zero.

Implementação da rotina de unfolding para determinação de distribuição de tamanho de grãos esféricos via distribuição de interceptos lineares e de área de seção

Ferreira Filho, Antonio Evangelista
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
46.18%
Na unfolding method of linear intercept distributions and secction área distribution was implemented for structures with spherical grains. Although the unfolding routine depends on the grain shape, structures with spheroidal grains can also be treated by this routine. Grains of non-spheroidal shape can be treated only as approximation. A software was developed with two parts. The first part calculates the probability matrix. The second part uses this matrix and minimizes the chi-square. The results are presented with any number of size classes as required. The probability matrix was determined by means of the linear intercept and section area distributions created by computer simulation. Using curve fittings the probability matrix for spheres of any sizes could be determined. Two kinds of tests were carried out to prove the efficiency of the Technique. The theoretical tests represent ideal cases. The software was able to exactly find the proposed grain size distribution. In the second test, a structure was simulated in computer and images of its slices were used to produce the corresponding linear intercept the section area distributions. These distributions were then unfolded. This test simulates better reality. The results show deviations from the real size distribution. This deviations are caused by statistic fluctuation. The unfolding of the linear intercept distribution works perfectly...

Phylogenetic relationships of human populations in sub-Saharan Africa

Weber, W.; Nash, D.; Motulsky, A.; Henneberg, M.; Crawford, M.; Martin, S.; Goldsmid, J.; Spedini, G.; Glidewell, S.; Schanfield, M.
Fonte: Wayne State Univ Press Publicador: Wayne State Univ Press
Tipo: Artigo de Revista Científica
Publicado em //2000 EN
Relevância na Pesquisa
55.88%
This study utilizes the GM/KM immunoglobulin allotype system to elucidate the phylogenetic relationships of sub-Saharan Africans. The importance of understanding the relatedness of these peoples stems from the sub-Saharan region being the possible birthplace of humans. Haplotype distributions were determined for 19 populations and compared using chi-square analysis. Published data of other sub-Saharan Africans and representative populations worldwide were also added for comparison. Genetic distances between populations were calculated based on haplotype frequencies, and genetic relationships were observed through principal components analysis. Data from the GM/KM system showed a genetic homogeneity of the Bantu populations, with some exceptions, supporting the possibility of a common origin of these peoples. The Malagasy appeared as a divergent population, most likely due to Southeast Asian/Austronesian admixture, as indicated by the presence of the GM*AF B haplotype. The Cape Coloured also showed a divergence, with their genetic structures containing Caucasoid and Khoisan contributions. Finally, the Mbuti Pygmies appeared genetically isolated and had the highest frequency of the GM*A B haplotype out of all studied populations.

Protocol for population testing of an Internet-based Personalised Decision Support system for colorectal cancer screening

Wilson, C.; Flight, I.; Zajac, I.; Turnbull, D.; Young, G.; Cole, S.; Gregory, T.
Fonte: BioMed Central Ltd Publicador: BioMed Central Ltd
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
55.88%
Background: Australia has a comparatively high incidence of colorectal (bowel) cancer; however, population screening uptake using faecal occult blood test (FOBT) remains low. This study will determine the impact on screening participation of a novel, Internet-based Personalised Decision Support (PDS) package. The PDS is designed to measure attitudes and cognitive concerns and provide people with individually tailored information, in real time, that will assist them with making a decision to screen. The hypothesis is that exposure to (tailored) PDS will result in greater participation in screening than participation following exposure to non-tailored PDS or resulting from the current non-tailored, paper-based approach. Methods/design: A randomised parallel trial comprising three arms will be conducted. Men and women aged 50-74 years (N = 3240) will be recruited. They must have access to the Internet; have not had an FOBT within the previous 12 months, or sigmoidoscopy or colonoscopy within the previous 5 years; have had no clinical diagnosis of bowel cancer. Groups 1 and 2 (PDS arms) will access a website and complete a baseline survey measuring decision-to-screen stage, attitudes and cognitive concerns and will receive immediate feedback; Group 1 will receive information 'tailored' to their responses in the baseline survey and group 2 will received 'non-tailored' bowel cancer information. Respondents in both groups will subsequently receive an FOBT kit. Group 3 (usual practice arm) will complete a paper-based version of the baseline survey and respondents will subsequently receive 'non-tailored' paper-based bowel cancer information with accompanying FOBT kit. Following despatch of FOBTs...

Chi-square approximation by Stein's method with application to Pearson's statistic

Gaunt, Robert E.; Pickett, Alastair; Reinert, Gesine
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/07/2015
Relevância na Pesquisa
56.05%
This paper concerns the development of Stein's method for chi-square approximation and its application to problems in statistics. New bounds for the derivatives of the solution of the gamma Stein equation are obtained. These bounds involve both the shape parameter and the order of the derivative. Subsequently Stein's method for chi-square approximation is applied to bound the distributional distance between Pearson's statistic and its limiting chi-square distribution, measured using smooth test functions. In combination with the use of symmetry arguments, Stein' method yields explicit bounds on this distributional distance of order $n^{-1}$.; Comment: 32 pages

Parameter Estimation in Astronomy with Poisson-Distributed Data. I. The Chi-Square-Gamma Statistic

Mighell, Kenneth J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/03/1999
Relevância na Pesquisa
46.25%
Applying the standard weighted mean formula, [sum_i {n_i sigma^{-2}_i}] / [sum_i {sigma^{-2}_i}], to determine the weighted mean of data, n_i, drawn from a Poisson distribution, will, on average, underestimate the true mean by ~1 for all true mean values larger than ~3 when the common assumption is made that the error of the ith observation is sigma_i = max(sqrt{n_i},1). This small, but statistically significant offset, explains the long-known observation that chi-square minimization techniques which use the modified Neyman's chi-square statistic, chi^2_{N} equiv sum_i (n_i-y_i)^2 / max(n_i,1), to compare Poisson-distributed data with model values, y_i, will typically predict a total number of counts that underestimates the true total by about 1 count per bin. Based on my finding that the weighted mean of data drawn from a Poisson distribution can be determined using the formula [sum_i [n_i + min(n_i,1)] (n_i+1)^{-1}] / [sum_i (n_i+1)^{-1}], I propose that a new chi-square statistic, chi^2_gamma equiv sum_i [n_i + min(n_i,1) - y_i]^2 / [n_i + 1], should always be used to analyze Poisson-distributed data in preference to the modified Neyman's chi-square statistic. I demonstrate the power and usefulness of chi-square-gamma minimization by using two statistical fitting techniques and five chi-square statistics to analyze simulated X-ray power-law 15-channel spectra with large and small counts per bin. I show that chi-square-gamma minimization with the Levenberg-Marquardt or Powell's method can produce excellent results (mean slope errors <=3%) with spectra having as few as 25 total counts.; Comment: 22 pages (LaTeX+aaspp4.sty)...

Parameter Estimation in Astronomy with Poisson-Distributed Data. II. The Modified Chi-Square-Gamma Statistic

Mighell, Kenneth J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/07/2000
Relevância na Pesquisa
56.19%
I investigate the use of Pearson's chi-square statistic, the Maximum Likelihood Ratio statistic for Poisson distributions, and the chi-square-gamma statistic (Mighell 1999, ApJ, 518, 380) for the determination of the goodness-of-fit between theoretical models and low-count Poisson-distributed data. I demonstrate that these statistics should not be used to determine the goodness-of-fit with data values of 10 or less. I modify the chi-square-gamma statistic for the purpose of improving its goodness-of-fit performance. I demonstrate that the modified chi-square-gamma statistic performs (nearly) like an ideal chi-square statistic for the determination of goodness-of-fit with low-count data. On average, for correct (true) models, the mean value of modified chi-square-gamma statistic is equal to the number of degrees of freedom (nu) and its variance is 2*nu --- like the chi-square distribution for nu degrees of freedom. Probabilities for modified chi-square-gamma goodness-of-fit values can be calculated with the incomplete gamma function. I give a practical demonstration showing how the modified chi-square-gamma statistic can be used in experimental astrophysics by analyzing simulated X-ray observations of a weak point source (signal-to-noise ratio of 5.2; 40 photons spread over 317 pixels) on a noisy background (0.06 photons per pixel). Accurate estimates (95% confidence intervals/limits) of the location and intensity of the X-ray point source are determined.; Comment: 40 pages (LaTeX+aaspp4.sty+flushrt.sty)...

Chi-square Intervals for a Poisson Parameter - Bayes, Classical and Structural

Maxwell, E. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/02/2011
Relevância na Pesquisa
56.05%
The 'standard' confidence interval for a Poisson parameter is only one of a number of estimation intervals based on the chi-square distribution that may be used in the estimation of the mean or mean rate for a Poisson model. Other chi-square intervals are available for experimenters using Bayesian or structural inference methods. Exploring these intervals also leads to other alternate approximate chi-square intervals. Although coverage probability may not always be of interest for Bayesian or structural intervals, coverage probabilities are useful for validating 'objective' priors. Coverage probabilities are explored for all of the intervals considered.; Comment: 14 pages

Chi-square simulation of the CIR process and the Heston model

Malham, Simon J. A.; Wiese, Anke
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.22%
The transition probability of a Cox-Ingersoll-Ross process can be represented by a non-central chi-square density. First we prove a new representation for the central chi-square density based on sums of powers of generalized Gaussian random variables. Second we prove Marsaglia's polar method extends to this distribution, providing a simple, exact, robust and efficient acceptance-rejection method for generalized Gaussian sampling and thus central chi-square sampling. Third we derive a simple, high-accuracy, robust and efficient direct inversion method for generalized Gaussian sampling based on the Beasley-Springer-Moro method. Indeed the accuracy of the approximation to the inverse cumulative distribution function is to the tenth decimal place. We then apply our methods to non-central chi-square variance sampling in the Heston model. We focus on the case when the number of degrees of freedom is small and the zero boundary is attracting and attainable, typical in foreign exchange markets. Using the additivity property of the chi-square distribution, our methods apply in all parameter regimes.; Comment: 32 pages, 6 figures, 8 tables, update

Moments of the log non-central chi-square distribution

Pav, Steven E.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/03/2015
Relevância na Pesquisa
66.05%
The cumulants and moments of the log of the non-central chi-square distribution are derived. For example, the expected log of a chi-square random variable with v degrees of freedom is log(2) + psi(v/2). Applications to modeling probability distributions are discussed.; Comment: 8 pages

Information Divergence is more chi squared distributed than the chi squared statistics

Harremoës, Peter; Tusnády, Gábor
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.23%
For testing goodness of fit it is very popular to use either the chi square statistic or G statistics (information divergence). Asymptotically both are chi square distributed so an obvious question is which of the two statistics that has a distribution that is closest to the chi square distribution. Surprisingly, when there is only one degree of freedom it seems like the distribution of information divergence is much better approximated by a chi square distribution than the chi square statistic. For random variables we introduce a new transformation that transform several important distributions into new random variables that are almost Gaussian. For the binomial distributions and the Poisson distributions we formulate a general conjecture about how close their transform are to the Gaussian. The conjecture is proved for Poisson distributions.; Comment: 5 pages, accepted for presentation at ISIT 2012

On the computation of moments of the partial non-central chi-squared distribution function

Gil, Amparo; Segura, Javier; Temme, Nico M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/06/2013
Relevância na Pesquisa
55.85%
Properties satisfied by the moments of the partial non-central chi-square distribution function, also known as Nuttall Q-functions, and methods for computing these moments are discussed in this paper. The Nuttall Q-function is involved in the study of a variety of problems in different fields, as for example digital communications.; Comment: 6 pages