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:: Search published articles ::
Showing 5 results for Bahrami Samani

Sayedeh Fatemeh Miri, Ehsan Bahrami Samani,
Volume 6, Issue 1 (8-2012)
Abstract

In this paper a general model is proposed for the joint distribution of nominal, ordinal and continuous variables with and without missing data. Closed forms are presented for likelihood functions of general location models. Also the Joe approximation is used for the parameters of general location models with mixed continuous, ordinal and nominal data with non-ignorable missing responses. To explain the ability of proposed models some simulation studies are performed and some real data are analyzed from a foreign language achievement study.

Masoumeh Esmailizadeh, Ehsan Bahrami Samani,
Volume 13, Issue 2 (2-2020)
Abstract

‎This paper will analyze inflated bivariate mixed count data‎. ‎The estimations of model parameters are obtained by the maximum likelihood method‎. ‎For a bivariate case which has inflation in one or two points‎, ‎the new bivariate inflated power series distributions are presented‎. ‎These inflated distributions are used in joint modeling of bivariate count responses‎. ‎Also‎, ‎to illustrate the utility of the proposed models‎, ‎some simulation studies are performed‎. ‎and finally‎, ‎a real dataset is analyzed‎.

Ehsan Bahrami Samani, Nafeseh Khojasteh Bakht,
Volume 14, Issue 1 (8-2020)
Abstract

In this paper‎, ‎the analysis of count response with many zeros‎, ‎named as zero-inflated data‎, ‎is considered‎. ‎Assumes that responses follow a zero-inflated power series distribution‎. ‎Because of there is missing of the type of random in the covariate‎, ‎some of the data application‎, ‎various methods for estimating of parameters by using the score function with and without missing data for the proposed regression model are presented‎. ‎On the other hand‎, ‎known or unknown selection probability in the missing covariates results in presenting a semi-parametric method for estimating of parameters in the zero-inflated power series regression model‎. ‎To illustrate the proposed method‎, ‎simulation studies and a real example are applied‎. ‎Finally‎, ‎the performance of the semi-parametric method is compared with maximum likelihood‎, ‎complete-case and inverse probability weighted method‎.

Mojtaba Zeinali, Ehsan Bahrami Samani,
Volume 15, Issue 1 (9-2021)
Abstract

This article aims to joint modeling of longitudinal CD4 cells count and time to death in HIV patients based on the AFT model. The modeling of the longitudinal count response, a GLME model under the family of PSD, was used. In contrast, for the TTE data, the parametric AFT model under the Weibull distribution was investigated. These two responses are linked through random effects correlated with the normal distribution. The longitudinal and survival data are then assumed independent, given the latent linking process and any available covariates. Considering excess zeros for two responses and right censoring, presented a joint model that has not yet been investigated by other researchers. The parameters were also estimated using MCMC methods.


Nastaran Sharifian, Ehsan Bahrami Samani,
Volume 15, Issue 2 (3-2022)
Abstract

One of the most frequently encountered longitudinal studies issues is data with losing the appointments or getting censoring. In such cases, all of the subjects do not have the same set of observation times. The missingness in the analysis of longitudinal discrete and continuous mixed data is also common, and missing may occur in one or both responses. Failure to pay attention to the cause of the missing (the mechanism of the missingness) leads to unbiased estimates and inferences. Therefore, in this paper, we investigate the mechanism of nonignorable missing in set-inflated continuous and zero-inflation power series, as well as the continuous and k-inflated ordinal mixed responses. A full likelihood-based approach is used to obtain the maximum likelihood estimates of the parameters of the models. In order to assess the performance of the models, some simulation studies are performed. Two applications of our models are illustrated for the American's Changing Lives  survey, and the Peabody Individual Achievement Test  data set.


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مجله علوم آماری – نشریه علمی پژوهشی انجمن آمار ایران Journal of Statistical Sciences

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