Letteratura scientifica selezionata sul tema "Test de Brown-Forsythe"

A maximum test in which the test statistic is the more extreme of the Brown-Forsythe and O’Brien’s test statistics is developed. Estimated Type I error rates and power are presented for the Brown-Forsythe test, O’Brien’s test, and the maximum test. For the conditions included in the study, Type I error rates for the maximum test are near the nominal level. In all conditions, the power of the maximum test tended to be equal to or greater than that of the test—O’Brien or Brown-Forsythe—that had the larger power.

Estimated Type I error rates and power are reported for a modified Fligner-Killeen test, O’Brien’s test, O’Brien’s test using Welch’s modified ANOVA, the Brown-Forsythe test, and two tests developed by Tiku. Normal and nonnormal distributions and a two-group design were investigated. O’Brien’s test and the Brown-Forsythe test had estimated Type I error rates near the nominal level for all conditions investigated. To maximize power when the sample sizes are equal, O’Brien’s test should be used with platykurtic distributions and the Brown-Forsythe test with leptokurtic distributions. Either test can be used when the kurtosis is zero. When the sample sizes are unequal, O’Brien’s test should be used with platykurtic distributions and the Brown-Forsythe with symmetric-leptokurtic distributions. With other distributions, the tests have similar power.

Estimated Type I error rates and power are reported for the Brown-Forsythe, O’Brien, Klotz, and Siegel-Tukey procedures. The effect of aligning the data, by using deviations from group means or group medians, is investigated for the latter two tests. Normal and non-normal distributions, equal and unequal sample-size combinations, and equal and unequal means are investigated for a two-group design. No test is robust and most powerful for all distributions, however, using O’Brien’s procedure will avoid the possibility of a liberal test and provide power almost as large as what would be provided by choosing the most powerful test for each distribution type. Using the Brown-Forsythe procedure with heavy-tailed distributions and O’Brien’s procedure for other distributions will increase power modestly and maintain robustness. Using the mean-aligned Klotz test or the unaligned Klotz test with appropriate distributions can increase power, but only at the risk of increased Type I error rates if the tests are not accurately matched to the distribution type.

Gene selection is an important issue in analyzing multiclass microarray data. Among many proposed selection methods, the traditional ANOVA F test statistic has been employed to identify informative genes for both class prediction (classification) and discovery problems. However, the F test statistic assumes an equal variance. This assumption may not be realistic for gene expression data. This paper explores other alternative test statistics which can handle heterogeneity of the variances. We study five such test statistics, which include Brown-Forsythe test statistic and Welch test statistic. Their performance is evaluated and compared with that of F statistic over different classification methods applied to publicly available microarray datasets.

A review of the literature has shown that robust procedures for testing variances have become available. The two best procedures are one proposed by O’Brien (1981) and another by Brown and Forsythe (1974). An examination of these procedures for a wide variety of populations confirms their robustness and indicates that optimal power can usually be obtained by applying a test for kurtosis to aid in the decision between these two procedures.

Background: Dental and Oral Therapist Functional Positions from CPNS formation are required to attend the training of the Dental and Oral Therapist Functional Positions first appointment in accordance with applicable regulations. Bapelkes Semarang as a training unit of the Ministry of Health held a Distance Training for 4 batches of Dental and Oral Therapists Functional Positions in 2022. The training aims to increase the knowledge of trainees in carrying out dental and oral health care. Objective: This study aims to analyze the effectiveness of Distance Training of Dental and Oral Therapist Functional Positions towards increasing the knowledge of trainees in dental and oral health care services. Methods: Quasi experimental design with the pretest-posttest one group design. The number of samples is a total population of 120 participants in the Distance Training of Dental and Oral Therapists Functional Positions in 2022. Data analysis used descriptive analysis and one-way ANOVA (Brown-Forsythe). Results: The descriptive test showed an increase in knowledge in each batch and the one-way ANOVA (Brown-Forsythe) statistical test showed a p value = 0.333 (p>0.05). It can be concluded that there is no significant difference in increasing knowledge among the four training batches. Conclusion: Distance Training of Dental and Oral Therapist Functional Positions is effectively increase the knowledge of trainees in dental and oral health care services.

A new two-sample test for comparing variability measures is proposed. To make the test robust and powerful, a new modified structural zero removal method is applied to the Brown–Forsythe transformation. The t-test-based statistic allows results to be expressed as the ratio of mean absolute deviations from median. Extensive simulation study demonstrates that the proposed test is robust to small or unequal sample sizes across many distributions. Moreover, careful exploratory analysis provides a new method for calculating the implicit association test scores for reaction time data with multiplicative treatment effects. Using this, a possible difference between variability of men and women’s implicit attitudes toward gay men is analyzed.

Some statistical tests, for example the analysis of variance, assume that variances are equal across groups or samples. Tests for homogeneity of variances can be used to verify that assumption and for pooling of data from different sources to yield an improved estimated variance. Tests for homogeneity of variances can be used usually under assumption of normal distributions or nearly normal distributions. In this paper some tests for homogeneity of variances are examined under the null hypothesis and under the alternative, for various sample sizes, for various symmetric and asymmetric distributions. Monte Carlo simulations has been used for this. In this paper the following procedures have been analyzed: Levene’a test, Brown-Forsythe test, Fligner-Killeen test and O’Brientest.

The study on the complexity of streamflow has guiding significance for hydrologic simulation, hydrologic prediction, water resources planning and management. Utilizing monthly streamflow data from four hydrologic control stations in the mainstream of the Weihe River in China, the methods of approximate entropy, sample entropy, two-dimensional entropy and fuzzy entropy are introduced into hydrology research to investigate the spatial distribution and dynamic change in streamflow complexity. The results indicate that the complexity of the streamflow has spatial differences in the Weihe River watershed, exhibiting an increasing tendency along the Weihe mainstream, except at the Linjiacun station, which may be attributed to the elevated anthropogenic influence. Employing sliding entropies, the variation points of the streamflow time series at the Weijiabu station were identified in 1968, 1993 and 2003, and those at the Linjiacun station, Xianyang station and Huaxian station occurred in 1971, 1993 and 2003. In the verification of the above points, the minimum value of t-test is 3.7514, and that of Brown–Forsythe is 7.0307, far exceeding the significance level of 95%. Also, the cumulative anomaly can detect two variation points. The t-test, Brown–Forsythe test and cumulative anomaly test strengthen the conclusion regarding the availability of entropies for identifying the streamflow variability. The results lead us to conclude that four entropies have good application effects in the complexity analysis of the streamflow time series. Moreover, two-dimensional entropy and fuzzy entropy, which have been rarely used in hydrology research before, demonstrate better continuity and relative consistency, are more suitable for short and noisy hydrologic time series and more effectively identify the streamflow complexity. The results could be very useful in identifying variation points in the streamflow time series.

The purpose of this thesis is to investigate day-of-the-week effects for stock index returns. The investigations include analysis of means and variances as well as return-distribution properties such as skewness and tail behavior. Moreover, the existences of conditional day-of-the-week effects, depending on the outcome of returns from the previous week, are analyzed. Particular emphasis is put on determining useful testing procedures for differences in variance in return data from different weekdays. Two time series models, AR and GARCH(1,1), are used to find out if any weekday's mean return is different from other days. The investigations are repeated for two-day re- turns and for returns of diversified portfolios made up of several stock index returns.

Les études d'association pan-génomiques (GWAS) ont révolutionné ces 15 dernières années la recherche en génétique humaine en permettant l'identification de milliers de variants génétiques associés à des maladies complexes comme les maladies cardiovasculaires et des traits biologiques comme des facteurs de la coagulation. Toutefois, ces études reposent principalement sur des modèles additifs qui ne permettent pas de capturer toute la complexité des mécanismes génétiques qui peuvent être mis en jeu. Les interactions entre gènes (épistasie), entre gènes et facteurs environnementaux ainsi que les effets épigénétiques dû à l’empreinte parentale, sont ainsi négligés. L'objectif principal de cette thèse est de détecter des effets génétiques non additifs dans des études d'association pan-génomiques sur les taux plasmatiques de 2 facteurs importants de la cascade de la coagulation : le facteur V et le facteur de Willebrand. Pour cela, une méthodologie statistique peu connue et reposant sur une modification du test de Brown-Forsythe a été utilisée dans plusieurs cohortes du consortium CHARGE. Cette méthodologie a permis d’identifier le locus PSKH2 comme nouvel acteur participant à la régulation des taux plasmatiques de Facteur V. L’application de cette stratégie de recherche aux taux plasmatiques de Facteur de Willebrand a mis en évidence les limites de la méthode en présence de plusieurs polymorphismes en déséquilibre de liaison et influençant le phénotype étudié. À l'avenir, il serait intéressant de poursuivre ces recherches en explorant d'autres facteurs de la coagulation et en utilisant d’autres méthodologies statistiques moins sujettes à l’influence du déséquilibre de liaison. Les études d’association pan-génomiques (GWAS) ont révolutionné ces 15 dernières années la recherche en génétique humaine en permettant l’identification de milliers de variants génétiques associés à des maladies complexes comme les maladies cardiovasculaires et des traits biologiques comme des facteurs de la coagulation. Toutefois, ces études reposent principalement sur des hypothèses d’effets génétiques additifs qui ne permettent pas de capturer toute la complexité des mécanismes génétiques qui peuvent être mis en jeu. Les interactions entre gènes (épistasie), entre gènes et facteurs environnementaux ainsi que les effets épigénétiques dus par exemple à l’empreinte parentale, sont ainsi négligés. L’objectif principal de cette thèse est de détecter des effets génétiques non additifs influençant les taux plasmatiques de 2 facteurs importants de la cascade de la coagulation : le Facteur V et le Facteur de von Willebrand, et ce à partir de données génétiques pan-génomiques. Pour cela, une méthodologie statistique peu connue et reposant sur une modification du test de Brown-Forsythe a été utilisée dans plusieurs cohortes du consortium CHARGE. Cette méthodologie a permis d’identifier le locus PSKH2 comme nouvel acteur participant à la régulation des taux plasmatiques de Facteur V. L’application de cette stratégie de recherche aux taux plasmatiques de Facteur de von Willebrand a mis en évidence les limites de la méthode en présence de plusieurs polymorphismes en déséquilibre de liaison et influençant le phénotype étudié. À l’avenir, il serait intéressant de poursuivre ces recherches en explorant d’autres facteurs de la coagulation et en utilisant d’autres méthodologies statistiques moins sujettes à l’influence du déséquilibre de liaison
Genome-wide association studies (GWAS) have revolutionized human genetics research over the past 15 years by enabling the identification of thousands of genetic variants associated with complex diseases, such as cardiovascular diseases, and biological traits, such as coagulation factors. However, these studies primarily rely on additive models, which do not capture the full complexity of genetic mechanisms that may be involved. Interactions between genes (epistasis), gene-environment interactions, and epigenetic effects such as those due to parental imprinting are thus neglected. The main objective of this thesis is to detect, from GWAS data, non-additive genetic effects on plasma levels of two important factors in the coagulation cascade: Factor V and von Willebrand Factor. To achieve this, a neglected statistical methodology based on a modification of the Brown-Forsythe test was applied in several cohorts from the CHARGE consortium. This methodology identified the PSKH2 locus as a novel player in the regulation of plasma Factor V levels. Applying this research strategy to von Willebrand Factor plasma levels highlighted the limitations of the method in the presence of multiple polymorphisms in linkage disequilibrium that influence the studied phenotype. In the future, it would be interesting to pursue this research by exploring other coagulation factors and using other statistical methodologies less subject to the influence of linkage disequilibrium

Understanding the learning online students acquire through online course experiences is important as online course options and availability continue to expand. This study seeks to compare problem-solving techniques and course learning outcomes of Calculus students through the comparison of work completed by online and face-to-face Calculus students. Four assessment questions, regarding integration, will be reviewed in an effort to distinguish commonalities and/or differences in understanding and problem-solving strategies deployed by online and face-to-face Calculus students. Statistical analyses of question scores will include usage of Levene's test, Welch test, Brown-Forsythe test, and F-test. A qualitative analysis will also be conducted to analyze problem-solving strategies used by the online and face-to-face Calculus students.

Understanding the learning online students acquire through online course experiences is important as online course options and availability continue to expand. This study seeks to compare problem-solving techniques and course learning outcomes of Calculus students through the comparison of work completed by online and face-to-face Calculus students. Four assessment questions, regarding integration, will be reviewed in an effort to distinguish commonalities and/or differences in understanding and problem-solving strategies deployed by online and face-to-face Calculus students. Statistical analyses of question scores will include usage of Levene's test, Welch test, Brown-Forsythe test, and F-test. A qualitative analysis will also be conducted to analyze problem-solving strategies used by the online and face-to-face Calculus students.