scholarly journals Rayleigh Mixture Distribution

2011 ◽  
Vol 2011 ◽  
pp. 1-17 ◽  
Author(s):  
Rezaul Karim ◽  
Pear Hossain ◽  
Sultana Begum ◽  
Forhad Hossain
Keyword(s):  
Method Of Moments ◽  
Mixture Distribution ◽  
Characteristic Functions ◽  
Weight Functions ◽  
Mixture Distributions ◽  
Chi Square ◽  
Exact Probability ◽  
Mixtures Of Distributions ◽  
Sampling Distributions ◽  
Shape Characteristics

This paper presents Rayleigh mixtures of distributions in which the weight functions are assumed to be chi-square, and sampling distributions. The exact probability density functions of the mixture of two correlated Rayleigh random variables have been derived. Different moments, characteristic functions, shape characteristics, and the estimates of the parameters of the proposed mixture distributions using method of moments have also been provided.

F-Test Alternatives to Fisher’s Exact Test and to the Chi-Square Test of Homogeneity in 2 × 2 Tables

1983 ◽  
Vol 8 (1) ◽  
pp. 59-73 ◽  
Author(s):  
John E. Overall ◽  
Robert R. Starbuck
Keyword(s):  
Beta Distribution ◽  
Binary Response ◽  
Binomial Model ◽  
Chi Square ◽  
Exact Probability ◽  
Exact Test ◽  
Mutual Dependence ◽  
Treatment Groups ◽  
Test Of Homogeneity ◽  
Chi Square Test

A binomial model is proposed for testing the significance of differences in binary response probabilities in two independent treatment groups. Without correction for continuity, the binomial statistic is essentially equivalent to Fisher’s exact probability. With correction for continuity, the binomial statistic approaches Pearson’s chi-square. Due to mutual dependence of the binomial and F distributions on the beta distribution, a simple F statistic can be used for computation instead of the binomial.

scholarly journals Parameter Estimation Method of Mixture Distribution for Construction Machinery

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Xinting Zhai ◽  
Jixin Wang ◽  
Jinshi Chen
Keyword(s):  
Parameter Estimation ◽  
Likelihood Function ◽  
Estimation Method ◽  
Mixture Distribution ◽  
Information Criterion ◽  
Working Environment ◽  
Practical Case ◽  
Chi Square ◽  
Construction Machinery ◽  
Parameter Estimation Method

Due to the harsh working environment of the construction machinery, a simple distribution cannot be used to approximate the shape of the rainflow matrix. In this paper, the Weibull-normal (W-n) mixture distribution is used. The lowest Akaike information criterion (AIC) value is employed to determine the components number of the mixture. A parameter estimation method based on the idea of optimization is proposed. The method estimates parameters of the mixture by maximizing the log likelihood function (LLF) using an intelligent optimization algorithm (IOA), genetic algorithm (GA). To verify the performance of the proposed method, one of the already existing methods is applied in the simulation study and the practical case study. The fitting effects of the fitted distributions are compared by calculating the AIC and chi-square (χ2) value. It can be concluded that the proposed method is feasible and effective for parameter estimation of the mixture distribution.

An Epidemiologic Study of Tongue Lesions in 1901 Iranian Dental Outpatients

2008 ◽  
Vol 9 (7) ◽  
pp. 73-80 ◽  
Author(s):  
Mina Motallebnejad ◽  
Neda Babaee ◽  
Shirin Sakhdari ◽  
Maryam Tavasoli
Keyword(s):  
Oral Hygiene ◽  
Strong Association ◽  
Epidemiologic Study ◽  
Black Tea ◽  
Epidemiological Survey ◽  
Poor Oral Hygiene ◽  
Chi Square ◽  
Northern Iran ◽  
Exact Probability ◽  
Epidemiologic Survey

Abstract Aim The aim of this study was to assess the frequency of nine tongue conditions and evaluate their relationship to oral hygiene status and personal habits in a Northern Iranian population. Methods and Materials This descriptive study evaluated 1901 healthy subjects (1142 women, 759 men) >12 years who were referred to the Dental Faculty of Babol University during a period from February 2005 to July 2006. A questionnaire was designed according to the aims of the study. Each subject completed the questionnaire and received a complete dental and oral examination. Statistical analysis was performed using SPSS software and Chi-square and Fisher's exact probability tests. Results Six hundred seventy-two (35.3%) of 1901 subjects had tongue lesions with a frequency of 38.6% in women and 47.7% in men which was statistically significant (P<0.0001). A strong association was found between tongue lesions and smoking (p<0.0001), black tea drinking (p=0.021), and poor oral hygiene (p<0.0001). Hairy tongue (p<0.0001), coated tongue (p<0.0001), and fissured tongue (p=0.014) conditions were significantly higher in males, while crenation of the tongue was more frequent in women (p<0.0001). Conclusion This epidemiologic survey of adult dental outpatients of Northern Iran assessing tongue conditions and lesions found the frequency of these conditions in 47.7% of males and 38.6% of females in this population. Tongue conditions and lesions were more frequent among smokers, black tea drinkers, and those with poor oral hygiene. The results of this epidemiological survey can only be interpreted for the population studied and as such cannot be generalized to the wider population of Iran, but future studies should be designed to assess the frequency of these conditions on a countrywide basis. Clinical Significance The results of this study suggest efficient oral hygiene programs and encouraging people to drink less tea and quit smoking may reduce tongue lesions in adult dental outpatients in Northern Iran. Citation Motallebnejad M, Babaee N, Sakhdari S, Tavasoli M. An Epidemiologic Study of Tongue Lesions in 1901 Iranian Dental Outpatients. J Contemp Dent Pract 2008 November; (9)7:073-080.

scholarly journals Dcmd: Distance-based classification using mixture distributions on microbiome data

2021 ◽  
Vol 17 (3) ◽  
pp. e1008799
Author(s):  
Konstantin Shestopaloff ◽  
Mei Dong ◽  
Fan Gao ◽  
Wei Xu
Keyword(s):  
Machine Learning ◽  
Count Data ◽  
Human Microbiome ◽  
Mixture Distribution ◽  
Classification Performance ◽  
Study Data ◽  
Mixture Distributions ◽  
Learning Approaches ◽  
Nearest Neighbours ◽  
Microbiome Data

Current advances in next-generation sequencing techniques have allowed researchers to conduct comprehensive research on the microbiome and human diseases, with recent studies identifying associations between the human microbiome and health outcomes for a number of chronic conditions. However, microbiome data structure, characterized by sparsity and skewness, presents challenges to building effective classifiers. To address this, we present an innovative approach for distance-based classification using mixture distributions (DCMD). The method aims to improve classification performance using microbiome community data, where the predictors are composed of sparse and heterogeneous count data. This approach models the inherent uncertainty in sparse counts by estimating a mixture distribution for the sample data and representing each observation as a distribution, conditional on observed counts and the estimated mixture, which are then used as inputs for distance-based classification. The method is implemented into a k-means classification and k-nearest neighbours framework. We develop two distance metrics that produce optimal results. The performance of the model is assessed using simulated and human microbiome study data, with results compared against a number of existing machine learning and distance-based classification approaches. The proposed method is competitive when compared to the other machine learning approaches, and shows a clear improvement over commonly used distance-based classifiers, underscoring the importance of modelling sparsity for achieving optimal results. The range of applicability and robustness make the proposed method a viable alternative for classification using sparse microbiome count data. The source code is available at https://github.com/kshestop/DCMD for academic use.

A Monte Carlo Comparison of Maximum Likelihood and Minimum Chi Square Sampling Distributions in Logit Analysis

Biometrics ◽  
1984 ◽  
Vol 40 (2) ◽  
pp. 471 ◽  
Author(s):  
Kimberly C. Smith ◽  
N. E. Savin ◽  
Jacqueline L. Robertson
Keyword(s):  
Monte Carlo ◽  
Maximum Likelihood ◽  
Logit Analysis ◽  
Chi Square ◽  
Sampling Distributions

scholarly journals Metabolomics Based Mechanism Exploration of Pulmonary Arterial Hypertension pathogenesis: Novel Lessons from Explanted Lungs

2021 ◽  
Author(s):  
Jingjing Ding ◽  
Chunyan Chu ◽  
Zhengsheng Mao ◽  
Jiawen Yang ◽  
Jie Wang ◽  
...  
Keyword(s):  
Pulmonary Arterial Hypertension ◽  
Arterial Hypertension ◽  
Metabolic Pathways ◽  
Molecular Mechanisms ◽  
Akt Pathway ◽  
Analysis Model ◽  
Chi Square ◽  
Exact Probability ◽  
Lung Cancer Patients ◽  
Pulmonary Arterial

Abstract Background: Metabolic pathways have been shown to participate in the pathogenesis of pulmonary arterial hypertension (PAH). We investigated the metabolic profile shifts to reveal molecular mechanisms underlying PAH. Methods: Explanted human lung tissues from 18 PAH patients were collected. The lung tissues far from the tumor from 16 lung cancer patients were taken as controls. Lung tissues were analyzed by LC-MS/MS based non-target metabolomics method. Pathway analysis was performed with KEGG database and MetaboAnalyst 5.0. Statistical analysis including partial least squares discriminant analysis (PLS-DA), Student’s t-test, Pearson’s correlation, Chi-square test and Fisher’s exact probability test were used. COX survival analysis model was applied to evaluate the predictive value of metabolites on prognosis. Protein expression levels were detected by Western blotting in human PAH lung tissues, rat monocrotaline-PAH lungs and hypoxia exposed human pulmonary artery smooth muscle cells (HPASMCs) to study the molecular mechanisms.Results: Significant differences in metabolites and metabolic pathways were identified among PAH subgroups and control tissues. Spermine levels were positively correlated with the patients' cardiac outputs (COs). Levels of (2e)-2,5-dichloro-4-oxo-2-hexenedioic acid were positively correlated with the patient's serum creatinine (Scr) levels. Patients with higher levels of thymine had a better prognosis. Moreover, 7 differential metabolites were associated with AKT pathway. AKT pathway inactivation was confirmed in human and rat PAH lungs and hypoxia exposed HPASMCs.Conclusions: Our findings provide the first metabolomics evidence for PAH pathogenesis by human lungs and may contribute to the improvement of therapeutic strategy.

scholarly journals A morphing approach for continuous generalization of linear map features

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243328
Author(s):  
Aji Gao ◽  
Jingzhong Li ◽  
Kai Chen
Keyword(s):  
Shape Matching ◽  
Map Generalization ◽  
Shape Context ◽  
Chi Square ◽  
Linear Map ◽  
Continuous Map ◽  
Shape Structure ◽  
Limited Scale ◽  
Map Data ◽  
Shape Characteristics

With the development of web maps, people are no longer satisfied with fixed and limited scale map services but want to obtain personalized and arbitrary scale map data. Continuous map generalization technology can be used to generate arbitrary scale map data. This paper proposes a morphing method for continuously generalizing linear map features using shape context matching and hierarchical interpolation (SCM-HI). More specifically, shape characteristics are quantitatively described by shape context on which shape similarity is measured based on a chi-square method; then, two levels of interpolation, skeleton and detail interpolations, are employed to generate the geometry of intermediate curves. The main contributions of our approach include (1) exploiting both the geometry and spatial structure of a vector curve in shape matching by using shape context, and (2) preserving both the main shape structure as-rigid-as-possible and local geometric details as gradual and smooth as possible for intermediate curves by hierarchical interpolation. Experiments show that our method generates plausible morphing effects and can thus serve as a robust approach for continuous generalization of linear map features.

Erlang mixture distribution with application on COVID-19 cases in egypt

2021 ◽  
pp. 2150015
Author(s):  
M. M. E. Abd El-Monsef
Keyword(s):  
Hazard Function ◽  
Mixture Distribution ◽  
Real Data ◽  
Finite Mixture ◽  
Erlang Distribution ◽  
Parameter Estimates ◽  
Proposed Model ◽  
Shape Characteristics ◽  
Erlang Distributions ◽  
Special Case

In this paper, a finite mixture of m-Erlang distributions is proposed. Different moments, shape characteristics and parameter estimates of the proposed model are also provided. The proposed mixture has the property that it has a bounded hazard function. A special case of the mixed Erlang distribution is introduced and discussed. In addition, a predictive technique is introduced to estimate the needed number of mixture components to fit a certain data. A real data concerning the confirmed COVID-19 cases in Egypt is introduced to utilize the predictive estimation technique. Two more real datasets are used to examine the flexibility of the proposed model.

scholarly journals Goats as alternative hosts of cattle ticks

2007 ◽  
Vol 74 (1) ◽  
Author(s):  
N. Nyangiwe ◽  
I.G. Horak
Keyword(s):  
Rhipicephalus Appendiculatus ◽  
Tick Control ◽  
Control Programme ◽  
Boophilus Microplus ◽  
Eastern Region ◽  
Eastern Cape ◽  
Chi Square ◽  
Exact Probability ◽  
Cattle Ticks ◽  
Chi Square Test

The objective of this study was to compare the presence on goats and cattle of adult ticks that usually infest cattle. To this end ticks collected from sets of five goats were compared with those collected from sets of five cattle at 72 communal dip-tanks in the eastern region of the Eastern Cape Province. Amblyomma hebraeum was present on goats at 25 and on cattle at 39 dip-tanks, and a total of 61 goats and 138 cattle were infested. Adult Rhipicephalus (Boophilus) microplus was present on goats at 48 and on cattle at 69 dip-tanks, and a total of 113 goats and 242 cattle were infested. The lengths of 84 of 148 female R. (Boophilus) microplus collected from the goats exceeded 5 mm or more, indicating that they could successfully engorge on these animals. The differences between the proportions of dip-tanks at which A. hebraeum or R. (Boophilus) microplus was present on goats and cattle and also between the proportions of goats and cattle that were infested were significant (Chi square test, P < 0.01). Adult Rhipicephalus appendiculatus was present on goats at 70 and on cattle at 67 dip-tanks, and a total of 296 goats and 271 cattle were infested. The proportion of dip-tanks at which cattle were infested did not differ significantly from the proportion of tanks at which goats were infested (Fischer's exact probability test, P = 0.44), but the proportion of infested cattle was significantly lower than the proportion of infested goats (Chi-square test, P < 0.05). Adult Rhipicephalus evertsi evertsi was present on goats and cattle at all 72 sampling localities, and a total of 334 goats and 316 cattle were infested. The proportion of infested cattle was significantly lower than the proportion of infested goats (Chi-square test, P < 0.05). These results underscore the necessity of including goats in any tick control programme designed for cattle at the same locality.

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