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Estudo estatístico do desempenho analítico das técnicas eletroquímicas VPD, VOQ e MVOQ para a redução do herbicida paraquat em UME-Au e sua quantificação em águas puras e naturais; Statistic study of the analytical performance of DPV, SWV and MSWV electrochemical techniques for the reduction of the paraquat herbicide on an Au-UME and its analysis and quantification in pure and natural waters

Silva, Osmair Benedito da
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 30/01/2008 Português
Relevância na Pesquisa
35.95%
Neste trabalho foi realizado um estudo estatístico do desempenho analítico das técnicas eletroquímicas Voltametria de pulso diferencial (VPD), Voltametria de onda quadrada (VOQ) e Voltametria de múltiplas ondas quadradas (VMOQ) para a redução do herbicida paraquat em ultramicroeletrodo de ouro (UME-Au) e sua análise e quantificação em águas puras e naturais. Os estudos da redução eletroquímica do paraquat foram realizados em eletrólito de suporte Na2SO4 0,1 mol L-1 em pH = 5,5. Os resultados mostraram a presença de dois picos de redução bem definidos , com o pico 1 em -0,64 V e o pico 2 em -0,94 V vs Ag/AgCl 3,0 mol L-1. Para as análises foi utilizado o pico 1 que é referente a uma reação em solução, onde a superfície eletródica serve apenas como intermediadora na transferência eletrônica. Utilizando-se os parâmetros experimentais e voltamétricos otimizados, curvas de trabalho foram construídas em eletrólito de suporte preparado com água ultrapurificada. Para a VPD, VOQ e VMOQ, os limites de detecção encontrados utilizando-se o método descrito em Miller & Miller e considerando-se o pico 1 foram: 55,35 ± 0,18 µg L-1 , 37,50 ± 0,32 µg L-1 e 21,42 ± 0,51 µg L-1, respectivamente. A metodologia foi aplicada em amostras de águas coletadas no Rio Mogi-Guaçu na cidade de São Carlos-SP. A variação da inclinação das curvas de trabalho obtida nas análises destas amostras foi praticamente insignificante em relação àquela obtida utilizando-se o eletrólito de suporte preparado com água ultrapurificada para as três técnicas utilizadas...

O ensino de informática aplicada nos cursos de graduação em arquitetura e urbanismo no Brasil; The teaching of applied Information technology in brazilian undergraduate courses of architecture and urbanism

Natumi, Yone
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 28/08/2013 Português
Relevância na Pesquisa
36.03%
O requisito da Informática na Arquitetura, em face da ausência de definição desse termo nas legislações pertinentes, motivou o desenvolvimento desta pesquisa. O objetivo foi analisar o ensino das disciplinas de Informática Aplicada à Arquitetura nos cursos de graduação em Arquitetura e Urbanismo. A metodologia de pesquisa adotada foi o levantamento de campo para verificar como os cursos brasileiros de graduação em Arquitetura e Urbanismo interpretam o termo ao ofertar as disciplinas de conteúdo identificado como sendo de Informática Aplicada, que foi inserida pela Portaria MEC nº 1.770/1994, uma vez que as instituições de ensino superior (IES) possuem autonomia e flexibilidade para estruturar as diretrizes curriculares de seus projetos pedagógicos. As IES e seus respectivos cursos de graduação em Arquitetura e Urbanismo foram obtidos no sistema e-MEC do Ministério da Educação. O universo desta pesquisa, as disciplinas de Informática Aplicada foram pesquisadas nos sítios eletrônicos de cada IES. Com o intuito de conhecer o perfil dos professores para ministrar as disciplinas de Informática Aplicada foi utilizado um aplicativo de Questionário on-line aos mesmos. Os currículos de cada um dos que responderam ao questionário foram analisados na plataforma Lattes. Os resultados da pesquisa revelaram as diversas nomenclaturas para a disciplina Informática Aplicada e conteúdos diferentes para a mesma denominação em vários cursos de Arquitetura e Urbanismo. Analisando-se as ementas...

A test statistic to detect errors in sib-pair relationships.

Ehm, M; Wagner, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1998 Português
Relevância na Pesquisa
26.15%
Several authors have proposed algorithms to detect Mendelian errors in human genetic linkage data. Most currently available methods use likelihood-based methods on multiplex family data to identify typing or pedigree errors. These algorithms cannot be applied in many sib-pair collections, because of lack of parental-genotype information. Nonetheless, misspecifying the relationships between individuals has serious consequences for sib-pair linkage studies: false relationships bias the statistics designed to identify linkage with disease phenotypes. To test the hypothesis that two individuals are sibs, we propose a test statistic based on the summation, over a large number of genetic markers, of the number of alleles shared identical by state by a pair of individuals, for each marker. The test statistic has an approximately normal distribution under the null hypothesis, and extreme negative values correspond to nonsib pairs. Power and significance studies show that the test statistic calculated by use of 50 unlinked markers has 96% power to detect half-sibs and has 100% power to detect unrelated individuals as not full-sib pairs, with a 5% false-positive rate. Furthermore, extreme positive values of the test statistic identify sibs as MZ twins.

A model-adjusted space-time scan statistic with an application to syndromic surveillance.

Kleinman, K. P.; Abrams, A. M.; Kulldorff, M.; Platt, R.
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Artigo de Revista Científica
Publicado em /06/2005 Português
Relevância na Pesquisa
26.11%
The space-time scan statistic is often used to identify incident disease clusters. We introduce a method to adjust for naturally occurring temporal trends or geographical patterns in illness. The space-time scan statistic was applied to reports of lower respiratory complaints in a large group practice. We compared its performance with unadjusted populations from: (1) the census, (2) group-practice membership counts, and on adjustments incorporating (3) day of week, month, and holidays; and (4) additionally, local history of illness. Using a nominal false detection rate of 5%, incident clusters during 1 year were identified on 26, 22, 4 and 2% of days for the four populations respectively. We show that it is important to account for naturally occurring temporal and geographic trends when using the space-time scan statistic for surveillance. The large number of days with clusters renders the census and membership approaches impractical for public health surveillance. The proposed adjustment allows practical surveillance.

The role of the c-statistic in variable selection for propensity score models

Westreich, Daniel; Cole, Stephen R.; Funk, Michele Jonsson; Brookhart, M. Alan; Stürmer, Til
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.11%
The applied literature on propensity scores has often cited the c-statistic as a measure of the ability of the propensity score to control confounding. However, a high c-statistic in the propensity model is neither necessary nor sufficient for control of confounding. Moreover, use of the c-statistic as a guide in constructing propensity scores may result in less overlap in propensity scores between treated and untreated subjects; this may require the analyst to restrict populations for inference. Such restrictions may reduce precision of estimates and change the population to which the estimate applies. Variable selection based on prior subject matter knowledge, empirical observation, and sensitivity analysis is preferable and avoids many of these problems.

Local multiplicity adjustment for the spatial scan statistic using the Gumbel distribution

Gangnon, Ronald E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.15%
The spatial scan statistic is an important and widely used tool for cluster detection. It is based on the simultaneous evaluation of the statistical significance of the maximum likelihood ratio test statistic over a large collection of potential clusters. In most cluster detection problems, there is variation in the extent of local multiplicity across the study region. For example, using a fixed maximum geographic radius for clusters, urban areas typically have many overlapping potential clusters, while rural areas have relatively few. The spatial scan statistic does not account for local multiplicity variation. We describe a previously proposed local multiplicity adjustment based on a nested Bonferroni correction and propose a novel adjustment based on a Gumbel distribution approximation to the distribution of a local scan statistic. We compare the performance of all three statistics in terms of power and a novel unbiased cluster detection criterion. These methods are then applied to the well-known New York leukemia dataset and a Wisconsin breast cancer incidence dataset.

A Scan Statistic for Binary Outcome Based on Hypergeometric Probability Model, with an Application to Detecting Spatial Clusters of Japanese Encephalitis

Zhao, Xing; Zhou, Xiao-Hua; Feng, Zijian; Guo, Pengfei; He, Hongyan; Zhang, Tao; Duan, Lei; Li, Xiaosong
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 13/06/2013 Português
Relevância na Pesquisa
26.25%
As a useful tool for geographical cluster detection of events, the spatial scan statistic is widely applied in many fields and plays an increasingly important role. The classic version of the spatial scan statistic for the binary outcome is developed by Kulldorff, based on the Bernoulli or the Poisson probability model. In this paper, we apply the Hypergeometric probability model to construct the likelihood function under the null hypothesis. Compared with existing methods, the likelihood function under the null hypothesis is an alternative and indirect method to identify the potential cluster, and the test statistic is the extreme value of the likelihood function. Similar with Kulldorff’s methods, we adopt Monte Carlo test for the test of significance. Both methods are applied for detecting spatial clusters of Japanese encephalitis in Sichuan province, China, in 2009, and the detected clusters are identical. Through a simulation to independent benchmark data, it is indicated that the test statistic based on the Hypergeometric model outweighs Kulldorff’s statistics for clusters of high population density or large size; otherwise Kulldorff’s statistics are superior.

Drug Adverse Event Detection in Health Plan Data Using the Gamma Poisson Shrinker and Comparison to the Tree-based Scan Statistic

Brown, Jeffrey S.; Petronis, Kenneth R.; Bate, Andrew; Zhang, Fang; Dashevsky, Inna; Kulldorff, Martin; Avery, Taliser R.; Davis, Robert L.; Chan, K. Arnold; Andrade, Susan E.; Boudreau, Denise; Gunter, Margaret J.; Herrinton, Lisa; Pawloski, Pamala A.; R
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.15%
Background: Drug adverse event (AE) signal detection using the Gamma Poisson Shrinker (GPS) is commonly applied in spontaneous reporting. AE signal detection using large observational health plan databases can expand medication safety surveillance. Methods: Using data from nine health plans, we conducted a pilot study to evaluate the implementation and findings of the GPS approach for two antifungal drugs, terbinafine and itraconazole, and two diabetes drugs, pioglitazone and rosiglitazone. We evaluated 1676 diagnosis codes grouped into 183 different clinical concepts and four levels of granularity. Several signaling thresholds were assessed. GPS results were compared to findings from a companion study using the identical analytic dataset but an alternative statistical method—the tree-based scan statistic (TreeScan). Results: We identified 71 statistical signals across two signaling thresholds and two methods, including closely-related signals of overlapping diagnosis definitions. Initial review found that most signals represented known adverse drug reactions or confounding. About 31% of signals met the highest signaling threshold. Conclusions: The GPS method was successfully applied to observational health plan data in a distributed data environment as a drug safety data mining method. There was substantial concordance between the GPS and TreeScan approaches. Key method implementation decisions relate to defining exposures and outcomes and informed choice of signaling thresholds.

Using the Reliable Change Index Statistic to Analyze Developmental Changes in Infants at Risk for Autism Spectrum Disorder

Barber, Rachel A.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
36.05%
Longitudinal studies of the development of autism spectrum disorders (ASD) provide an understanding of which variables may be important predictors of an ASD. The objective of the current study is to apply the reliable change index (RCI) statistic to examine whether the Parent Observation of Early Markers Scale (POEMS) is sensitive to developmental change, and whether these changes can be quantified along a child’s developmental trajectory. Ninety-six children with older siblings with autism were followed from 1-36 months of age. Group-based RCI analysis confirms that the POEMS is capable of detecting significant changes within pre-defined diagnostic groups. Within-subject analysis suggests that ongoing monitoring of a child at-risk for an ASD requires interpretation of both significant intervals identified by the RCI statistic, as well as the presence of repeated high (i.e., >70) scores. This study provides preliminary evidence for a reasonably sensitive and specific means by which individual change can be clinically monitored via parent report.

Simple and accurate one-sided inference from signed roots of likelihood ratios

DiCiccio, Thomas J; Martin, Michael; Stern, Steven E
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Working/Technical Paper Formato: 142414 bytes; application/pdf
Português
Relevância na Pesquisa
35.95%
The authors propose two methods based on the signed root of the likelihood ratio statistic for one-sided testing of a simple null hypothesis about a scalar parameter in the presence of nuisance parameters. Both methods are third-order accurate and utilise simulation to avoid the need for onerous analytical calculations characteristic of competing saddlepoint procedures. Moreover, the new methods do not require specification of ancillary statistics. The methods respect the conditioning associated with similar tests up to an error of third order, and conditioning on ancillary statistics to an error of second order.; no

HYPOTHESIS SETTING AND ORDER STATISTIC FOR ROBUST GENOMIC META-ANALYSIS

Song, Chi; Tseng, George C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
26.15%
Meta-analysis techniques have been widely developed and applied in genomic applications, especially for combining multiple transcriptomic studies. In this paper, we propose an order statistic of p-values (rth ordered p-value, rOP) across combined studies as the test statistic. We illustrate different hypothesis settings that detect gene markers differentially expressed (DE) “in all studies”, “in the majority of studies”, or “in one or more studies”, and specify rOP as a suitable method for detecting DE genes “in the majority of studies”. We develop methods to estimate the parameter r in rOP for real applications. Statistical properties such as its asymptotic behavior and a one-sided testing correction for detecting markers of concordant expression changes are explored. Power calculation and simulation show better performance of rOP compared to classical Fisher's method, Stouffer's method, minimum p-value method and maximum p-value method under the focused hypothesis setting. Theoretically, rOP is found connected to the naïve vote counting method and can be viewed as a generalized form of vote counting with better statistical properties. The method is applied to three microarray meta-analysis examples including major depressive disorder...

Saddlepoint approximation for Student's t-statistic with no moment conditions

Jing, Bing-Yi; Shao, Qi-Man; Zhou, Wang
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/08/2005 Português
Relevância na Pesquisa
26.15%
A saddlepoint approximation of the Student's t-statistic was derived by Daniels and Young [Biometrika 78 (1991) 169-179] under the very stringent exponential moment condition that requires that the underlying density function go down at least as fast as a Normal density in the tails. This is a severe restriction on the approximation's applicability. In this paper we show that this strong exponential moment restriction can be completely dispensed with, that is, saddlepoint approximation of the Student's t-statistic remains valid without any moment condition. This confirms the folklore that the Student's t-statistic is robust against outliers. The saddlepoint approximation not only provides a very accurate approximation for the Student's t-statistic, but it also can be applied much more widely in statistical inference. As a result, saddlepoint approximations should always be used whenever possible. Some numerical work will be given to illustrate these points.; Comment: Published at http://dx.doi.org/10.1214/009053604000000742 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Hypothesis setting and order statistic for robust genomic meta-analysis

Song, Chi; Tseng, George C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 31/07/2014 Português
Relevância na Pesquisa
26.2%
Meta-analysis techniques have been widely developed and applied in genomic applications, especially for combining multiple transcriptomic studies. In this paper we propose an order statistic of $p$-values ($r$th ordered $p$-value, rOP) across combined studies as the test statistic. We illustrate different hypothesis settings that detect gene markers differentially expressed (DE) 'in all studies," "in the majority of studies"' or "in one or more studies," and specify rOP as a suitable method for detecting DE genes "in the majority of studies." We develop methods to estimate the parameter $r$ in rOP for real applications. Statistical properties such as its asymptotic behavior and a one-sided testing correction for detecting markers of concordant expression changes are explored. Power calculation and simulation show better performance of rOP compared to classical Fisher's method, Stouffer's method, minimum $p$-value method and maximum $p$-value method under the focused hypothesis setting. Theoretically, rOP is found connected to the na\"{i}ve vote counting method and can be viewed as a generalized form of vote counting with better statistical properties. The method is applied to three microarray meta-analysis examples including major depressive disorder...

Spatio-Temporal Disease Surveillance: Forward Selection Scan Statistic

Sparks, Ross; Ickowicz, Adrien
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/09/2013 Português
Relevância na Pesquisa
26.11%
The scan statistic sets the benchmark for spatio-temporal surveillance methods with its popularity. In its simplest form it scans the target area and time to find regions with disease count higher than expected. If the shape and size of the disease outbreaks are known, then to detect it sufficiently early the scan statistic can design its search area to be efficient for this shape and size. A plan that is efficient at detecting a range of disease outbreak shapes and sizes is important because these vary from one outbreak to the next and are generally never known in advance. This paper offers a forward selection scan statistic that reduces the computational effort on the usual single window scan plan, while still offering greater flexibility in signalling outbreaks of varying shapes. The approach starts by dividing the target geographical regions into a lattice. Secondly it smooths the time series of lattice cell counts using multivariate exponential weighted moving averages. Thirdly, these EWMA cell counts are spatially smoothed to reduce spatial noise and leave the spatial signal. The fourth step uses forward selection approach to scanning mutually exclusive and exhaustive rectangular regions of dynamic dimensions. In the fifth step...

An adaptively weighted statistic for detecting differential gene expression when combining multiple transcriptomic studies

Li, Jia; Tseng, George C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.15%
Global expression analyses using microarray technologies are becoming more common in genomic research, therefore, new statistical challenges associated with combining information from multiple studies must be addressed. In this paper we will describe our proposal for an adaptively weighted (AW) statistic to combine multiple genomic studies for detecting differentially expressed genes. We will also present our results from comparisons of our proposed AW statistic to Fisher's equally weighted (EW), Tippett's minimum p-value (minP) and Pearson's (PR) statistics. Due to the absence of a uniformly powerful test, we used a simplified Gaussian scenario to compare the four methods. Our AW statistic consistently produced the best or near-best power for a range of alternative hypotheses. AW-obtained weights also have the additional advantage of filtering discordant biomarkers and providing natural detected gene categories for further biological investigation. Here we will demonstrate the superior performance of our proposed AW statistic based on a mix of power analyses, simulations and applications using data sets for multi-tissue energy metabolism mouse, multi-lab prostate cancer and lung cancer.; Comment: Published in at http://dx.doi.org/10.1214/10-AOAS393 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Robust New Statistic for fitting the Baryon Acoustic Feature

Osumi, Keisuke; Ho, Shirley; Eisenstein, Daniel J.; Vargas-Magaña, Mariana
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/05/2015 Português
Relevância na Pesquisa
26.21%
We investigate the utility and robustness of a new statistic, $\omega_{\ell}\left(r_{c}\right)$, for analyzing Baryon Acoustic Oscillations (BAO). We apply $\omega_{\ell}\left(r_{c}\right)$, introduced in Xu et al. (2010), to mocks and data from the Sloan Digital Sky Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey (BOSS) included in the SDSS Data Release Eleven (DR11). We fit the anisotropic clustering using the monopole and quadrupole of the $\omega_{\ell}\left(r_{c}\right)$ statistic in a manner similar to conventional multipole fitting methods using the correlation function as detailed in (Xu et al. 2012). To test the performance of the $\omega_{\ell}\left(r_{c}\right)$ statistic we compare our results to those obtained using the multipoles. The results are in agreement. We also conduct a brief investigation into some of the possible advantages of using the $\omega_{\ell}\left(r_{c}\right)$ statistic for BAO analysis. The $\omega_{\ell}\left(r_{c}\right)$ analysis matches the stability of the multipoles analysis in response to artificially introduced distortions in the data, without using extra nuisance parameters to improve the fit. When applied to data with systematics, the $\omega_{\ell}\left(r_{c}\right)$ statistic again matches the performance of fitting the multipoles without using nuisance parameters. In all the analyzed circumstances...

A Weighted U Statistic for Genetic Association Analyses of Sequencing Data

Wei, Changshuai; Li, Ming; He, Zihuai; Vsevolozhskaya, Olga; Schaid, Daniel J.; Lu, Qing
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/05/2015 Português
Relevância na Pesquisa
26.15%
With advancements in next generation sequencing technology, a massive amount of sequencing data are generated, offering a great opportunity to comprehensively investigate the role of rare variants in the genetic etiology of complex diseases. Nevertheless, this poses a great challenge for the statistical analysis of high-dimensional sequencing data. The association analyses based on traditional statistical methods suffer substantial power loss because of the low frequency of genetic variants and the extremely high dimensionality of the data. We developed a weighted U statistic, referred to as WU-seq, for the high-dimensional association analysis of sequencing data. Based on a non-parametric U statistic, WU-SEQ makes no assumption of the underlying disease model and phenotype distribution, and can be applied to a variety of phenotypes. Through simulation studies and an empirical study, we showed that WU-SEQ outperformed a commonly used SKAT method when the underlying assumptions were violated (e.g., the phenotype followed a heavy-tailed distribution). Even when the assumptions were satisfied, WU-SEQ still attained comparable performance to SKAT. Finally, we applied WU-seq to sequencing data from the Dallas Heart Study (DHS), and detected an association between ANGPTL 4 and very low density lipoprotein cholesterol.

A spatial scan statistic for zero-inflated Poisson process

Cançado, André L. F.; da-Silva, Cibele Q.; da Silva, Michel F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/11/2013 Português
Relevância na Pesquisa
26.18%
The scan statistic is widely used in spatial cluster detection applications of inhomogeneous Poisson processes. However, real data may present substantial departure from the underlying Poisson process. One of the possible departures has to do with zero excess. Some studies point out that when applied to data with excess zeros, the spatial scan statistic may produce biased inferences. In this work, we develop a closed-form scan statistic for cluster detection of spatial zero-inflated count data. We apply our methodology to simulated and real data. Our simulations revealed that the Scan-Poisson statistic steadily deteriorates as the number of zeros increases, producing biased inferences. On the other hand, our proposed Scan-ZIP and Scan-ZIP+EM statistics are, most of the time, either superior or comparable to the Scan-Poisson statistic.

A Preferred-Direction Statistic for Sky Maps

Bunn, Emory F.; Scott, Douglas
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.11%
Large patterns could exist on the microwave sky as a result of various non-standard possibilities for the large-scale Universe -- rotation or shear, non-trivial topology, and single topological defects are specific examples. All-sky (or nearly all-sky) CMB data sets allow us, uniquely, to constrain such exotica, and it is therefore worthwhile to explore a wide range of statistical tests. We describe one such statistic here, which is based on determining gradients and is useful for assessing the level of `preferred directionality' or `stripiness' in the map. This method is more general than other techniques for picking out specific patterns on the sky, and it also has the advantage of being easily calculable for the mega-pixel maps which will soon be available. For the purposes of illustration, we apply this statistic to the four-year COBE DMR data. For future CMB maps we expect this to be a useful statistical test of the large scale structure of the Universe. In principle, the same statistic could also be applied to sky maps at other wavelengths, to CMB polarisation maps, and to catalogues of discrete objects. It may also be useful as a means of checking for residual directionality (e.g., from Galactic or ecliptic signals) in maps.; Comment: Accepted to MNRAS. One new figure added; other relatively minor changes to match published version. No substantive changes to conclusions. 8 pages...

Accounting for spatial correlation in the scan statistic

Loh, Ji Meng; Zhu, Zhengyuan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/12/2007 Português
Relevância na Pesquisa
26.15%
The spatial scan statistic is widely used in epidemiology and medical studies as a tool to identify hotspots of diseases. The classical spatial scan statistic assumes the number of disease cases in different locations have independent Poisson distributions, while in practice the data may exhibit overdispersion and spatial correlation. In this work, we examine the behavior of the spatial scan statistic when overdispersion and spatial correlation are present, and propose a modified spatial scan statistic to account for that. Some theoretical results are provided to demonstrate that ignoring the overdispersion and spatial correlation leads to an increased rate of false positives, which is verified through a simulation study. Simulation studies also show that our modified procedure can substantially reduce the rate of false alarms. Two data examples involving brain cancer cases in New Mexico and chickenpox incidence data in France are used to illustrate the practical relevance of the modified procedure.; Comment: Published in at http://dx.doi.org/10.1214/07-AOAS129 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org)