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Showing 201 results for Type of Study: Research
Ali Shadrokh, Shahrastani Shahram Yaghoobzadeh,
Volume 22, Issue 2 (3-2018)
Abstract
In this paper, a new five-parameter so-called Beta-Gompertz Geometric (BGG) distribution is introduced that can have a decreasing, increasing, and bathtub-shaped failure rate function depending on its parameters. Some mathematical properties of the this distribution, such as the density and hazard rate functions, moments, moment generating function, R and Shannon entropy, Bonferroni and Lorenz curves and the mean deavations are provided. We discuss maximum likelihood estimation of the BGG parameters from one observed sample. At the end, in order to show the BGG distribution flexibility, an application using a real data set is presented.
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Volume 22, Issue 2 (3-2018)
Abstract
In this paper, a new probability distribution, based on the family of hyperbolic cosine distributions is proposed and its various statistical and reliability characteristics are investigated. The new category of HCF distributions is obtained by combining a baseline F distribution with the hyperbolic cosine function. Based on the base log-logistics distribution, we introduce a new distribution so-called HCLL and derive the various properties of the proposed distribution including the moments, quantiles, moment generating function, failure rate function, mean residual lifetime, order statistics and stress-strength parameter. Estimation of the parameters of HCLL for a real data set is investigated by using three methods: maximum likelihood, Bayesian and bootstrap (parametric and non-parametric). We evaluate the efficiency of the maximum likelihood estimation method by Monte Carlo simulation.
In addition, in the application section, by using a realistic data set, the superiority of HCLL model to generalized exponential, Weibull, hyperbolic cosine exponential, gamma, weighted exponential distributions is shown through the different criteria of selection model.
S Mahmoud Taheri, , , ,
Volume 23, Issue 1 (9-2018)
Abstract
This study aims to use a method of systemic review, called meta-analysis, to analysis the results of studies carried out in Iran about the role of self-regulation learning on learners’ academic performance in the past decade. So far studies investigating the relationship between self-learning and academic achievement have been conducted mainly in the frame of classical statistical models, while the nature of these variables and the relationship between them are fuzzy so that. It is suitable, therefore, to employ a fuzzy method to analysis such data. To do this 50 accomplished researches about the role of self-regulation learning on learners’ academic performance, 31 researches were chosen for fuzzy meta-analysis. The obtained results show that there is a meaningful relationship between self-regulation learning and learners’ academic achievement and self-regulation learning cam explain 4-17 percent of variance of the academic achievement. The obtain results can be use to education program planning and effective learning them.
Dr. Mehdi Shams,
Volume 23, Issue 1 (9-2018)
Abstract
In this paper we explain a necessary and sufficent condition for independence between any arbitrary statistics with sufficient statistics which is also maximum likelihood estimator in a general
exponential family with location and scale parameter namely generalized normal distribution. At the end, it is shown that the converse is true except in the asymptotic cases.
Mohsen Khosravi, Maryam Khajehhassani,
Volume 23, Issue 1 (9-2018)
Abstract
The Borel-Cantelli Lemma is very important in the probability theory. In this paper, we first describe the general case of the Borel-Cantelli Lemma. The first part of this lemma, assuming convergence and the second part includes divergence and independence assumptions. In the following, we have brought generalizations of the first and second part of this lemma. In most generalizations of part $amalg$, the condition of independence, pairwise independence, weakening and elimination of the condition of independence have been investigated.
Dr Mahdi Yousefi, Maryam Masoumi,
Volume 23, Issue 1 (9-2018)
Abstract
Due to the economical restrictions, improving efficiency in the collection and processing of blood products at blood centers is important. This study uses data envelopment analysis (DEA) to evaluate the efficiency of 31 Provincial units of Iranian Blood Transfusion Organizations (IBTO) to determine to what extent efficiency can be improved. Efficiency grades were computed with DEA linear programming techniques and Provincial units of IBTO characteristics that important affect efficiency determined for two consecutive years, 22 Provincial units of IBTO were efficient and 9 were inefficient. Otherwise based on PCA results, Efficiency was mainly affected by Number of BCPCs, BCCs, MTs, Efficiency did not directly relate to Population density of province, Number of donor beds and area of BTC. The major reason of inefficiency was excess allocating resulting from a suboptimal combination of Number of BCPCs, BCCs, and MTs.
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Volume 23, Issue 1 (9-2018)
Abstract
In this paper some properties of Beta - X family are discussed and a member of the family,the beta– normal distribution, is studied in detail.One real data set are used to illustrate the applications of the beta-normal distribution and compare that to gamma - normal and Birnbaum-Saunders distriboutions.
Miss Atefeh Karami,
Volume 23, Issue 1 (9-2018)
Abstract
The normal distribution plays an important role in statistical analysis. However, a researcher may also wish to construct another symmetric distributions which fit the data better than the normal distribution. For this purpose, more flexible distributions have been introduced. In this thesis, we introduce some of such distributions. We first introduce the slash distribution as a family of mixed-normal scale distributions. The slash distribution can be used instead of normal distribution, in many situations. We also introduce Skew-slash. Then, a new modified-slash distribution is discussed. We also study a modified Skew-slash distribution. Some properties of the distributions discussed in this thesis are given. In particular, we present the stochastic representations, density functions and moments of the distributions.
Shahrastani Shahram Yaghoobzadeh Shahrastani,
Volume 23, Issue 2 (3-2019)
Abstract
In this paper, a new estimate of exponential type of auxiliary information to help simple random sampling without replacement of the finite population mean is introduced. This new estimator with a few other estimates using two real data sets are compared with the mean square error.
Dr. Mehdi Shams,
Volume 23, Issue 2 (3-2019)
Abstract
In this paper, after introducing exponential family and a history of work done by researchers in the field of statistics, some applications of this family in statistical inference especially in estimation problem,statistical hypothesis testing and statistical information theory concepts will be discussed.
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Volume 23, Issue 2 (3-2019)
Abstract
In this paper, in order to establish a confidence interval (general and shortest) for quantiles of normal distribution in the case of one population, we present a pivotal quantity that has non-central t distribution. In the case of two independent normal populations, we construct a confidence interval for the difference quantiles based on the generalized pivotal quantity and introduce a simple method for extracting its percentiles, by which a shorter confidence interval can be constructed. We will also examine the performance of the proposed methods by using simulations and examples.
Mrs Azam Rastin, Dr Mohmmadreza Faridrohani, Dr Amirabbas Momenan, Dr Fatemeh Eskandari, Dr Davood Khalili,
Volume 23, Issue 2 (3-2019)
Abstract
Cardiovascular diseases (CVDs) are the leading cause of death worldwide. To specify an appropriate model to determine the risk of CVD and predict survival rate, users are required to specify a functional form which relates the outcome variables to the input ones. In this paper, we proposed a dimension reduction method using a general model, which includes many widely used survival models as special cases.
Using an appropriate combination of dimension reduction and Cox Proportional Hazards model, we found a method which is effective for survival prediction.
Javad Ahmadi, ,
Volume 23, Issue 2 (3-2019)
Abstract
A simultaneous confidence band gives useful information on the reasonable range of the unknown regression model. In this note, when the predictor variables are constrained to a special ellipsoidal region, hyperbolic and constant width confidence bonds for a multiple linear regression model are compared under the minimum volome confidence set (MVCS) criterion. The size of one speical angle that determines the size of the predictor variable region is used to find out which band is better than the other. When the angle and consquently the size of the predictor variable region is small, the constant width band is better than the hyperbolic band.
When the angle hence the size of the predictor variable regoin is large, the hyperbolic band is considerably better than the constant width band.
Mohamad Hosein Poursaeed,
Volume 23, Issue 2 (3-2019)
Abstract
The censored data are widely used in statistical tests and parameters estimation. In some cases e.g. medical accidents which data are not recorded at the time of occurrence, some methods such as interval censoring are used. In this paper, for a random sample uniformly distributed on the interval (0,θ) the interval censoring have been used. A consistent estimator of θ and some asymptotically confidence intervals for θ are presented.
Aliakbar Rasekhi,
Volume 23, Issue 2 (3-2019)
Abstract
WinBUGS is one of the usual softwares in computational Bayesian statistics, which is used to fit Baysian models easily. Although this software has usual mathematical functions and statistical distributions as built in functions, sometimes it is necessary to include other functions and distributions in computations which is done by some tricks and indirectly. By using WinBUGS development interface (known as WBDev), new mathematical functions and statistical distributions can be added in the software. This method facilitates writing codes of statistical models, increases speed of computations and make computations more efficient. In this paper, the stages of including new mathematical functions and statistical distributions in the WinBUGS are illustrated by some examples.
Atieh Shabaniyan Borujeni, iraj Kazemi,
Volume 24, Issue 1 (9-2019)
Abstract
A popular application of nonlinear models with mixed effects pharmacokinetic studies, in which the distribution of used drug during the life of the individual study. The fit of these models assume normality of the random effects and errors are common, but can not make it invalid results in the estimation. In longitudinal data analysis, typically assume that the random effects and random errors are normally distributed, but there is a possible violation of empirical studies. For this reason, the analysis of the pharmacokinetic data such as normal distribution, slashe, t - student and Contaminated normal considered to be based on analytical achieved. In this paper, parameter estimation of nonlinear models with mixed effects on the maximum likelihood estimation method and the Bayesian approach respectively by SAS software and Open Bugs pharmacokinetic data set for being carried out. Also, using the model selection criteria are based on these two approaches, we found the best fit model to the data.
Ali Shadrokh, Shahrastani Shahram Yaghoobzadeh,
Volume 24, Issue 1 (9-2019)
Abstract
In this study, E-Bayesian and hierarchical Bayesian of parameter of Rayleigh distribution under progressive type-II censoring sampales and the efficiency of the proposed methods has been compared with each and Bayesian estimator using Monte Carlo simulation.
Dr. Mehdi Shams, Dr. Gholamreza Hesamian,
Volume 24, Issue 1 (9-2019)
Abstract
In this paper after introduce Ito integral we discuss filtering problem. In filtering problem there are two stochastic differential equations (system and observation) that given the observations we must find the best estimate for the random process of the system based on these observations. At last we give some useful examples.
Shahrastani Shahram Yaghoobzadeh,
Volume 24, Issue 1 (9-2019)
Abstract
In this paper, reliability in multi-component stress-strength models, when the stress and strength variables are inverse Rayleigh distributions with different parameters of alpha and beta. Estimates of the maximum likelihood, Bayesian and empirical Bayesian are estimated. Then, with the help of Monte Carlo simulation and two real data sets, these estimation methods are compared.
Dr. Shahram Mansouri,
Volume 24, Issue 1 (9-2019)
Abstract
There is a one to one correspondence between renewal function and the probability density function of the times of observations of the successive occurrences of each renewal process. Furthermore, practical application of renewal processes requires renewal function information, and this function plays an essential role in the study of renewal processes behavior by which predictions could be made. In this paper, the renewal functions corresponding with two distributions with the times of successive observations distributed by Erlang (n,lambda) , and uniform (0,b) are determined by Laplace transform and its theorems. Finally, an application of the renewal process is presented in physics.
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