Truncated-exponential skew-symmetric distributions

The family of skew distributions introduced by Azzalini and extended by others has received widespread attention. However, it suffers from complicated inference procedures. In this paper, a new family of skew distributions that overcomes the difficulties is introduced. This new family belongs to the exponential family. Many properties of this family are studied, inference procedures developed and simulation studies performed to assess the procedures. Some particular cases of this family, evidence of its flexibility and a real data application are presented. At least 10 advantages of the new family over Azzalini's distributions are established.     

The minimum value of geometric-arithmetic index of graphs with minimum degree 2

The geometric-arithmetic index was introduced in the chemical graph theory and it has shown to be applicable. The aim of this paper is to obtain the extremal graphs with respect to the geometric-arithmetic index among all graphs with minimum degree 2. Let G(2, n) be the set of connected simple graphs on n vertices with minimum degree 2. We use linear programming formulation and prove that the minimum value of the first geometric-arithmetic \((GA_{1})\) index of G(2, n) is obtained by the following formula:

$$\begin{aligned} GA_1^* = \left\{ \begin{array}{ll} n&{}\quad n \le 24, \\ \mathrm{{24}}\mathrm{{.79}}&{}\quad n = 25, \\ \frac{{4\left( {n - 2} \right) \sqrt{2\left( {n - 2} \right) } }}{n}&{}\quad n \ge 26. \\ \end{array} \right. \end{aligned}$$

     

A Desire to Return to the Country of Birth as a Function of Language Preference: An Empirical Study with Iranian Immigrants in the United States

It was hypothesized that bilingual Iranian immigrants in the United States who prefer to use the Persian language, compared to Iranians who prefer to use English, would be more likely to express a desire to return to Iran to live. Participants were 292 bilingual Iranian immigrants in the United States (128 men, 164 women) who completed a questionnaire with a similar content, prepared in Persian on one side and in English on the other side. Participants were given the option to either complete the Persian or English version of the questionnaire. Results confirmed the research hypothesis suggesting that the immigrants’ preference in using their native language serves as a “pull” factor that increases the probability of a desire to return to the country of birth. It was also found that women and younger respondents were less likely to express a desire to return to Iran. Level of education, marital status, years of living in the United States, and attitudes toward marriage and the family did not predict such a desire. Implications for acculturation research and for counseling culturally diverse clients are discussed. Policy implications to attract immigrants back to their country of birth were also discussed.     

Bayesian analysis of covariance under inverse Gaussian model

This paper considers the problem of analysis of covariance (ANCOVA) under the assumption of inverse Gaussian distribution for response variable from the Bayesian point of view. We develop a fully Bayesian model for ANCOVA based on the conjugate prior distributions for parameters contained in the model. The Bayes estimator of parameters, ANCOVA model and adjusted effects for both treatments and covariates along with predictive distribution of future observations are developed. We also provide the essentials for comparing adjusted treatments effects and adjusted factor effects. A simulation study and a real world application are also performed to illustrate and evaluate the proposed Bayesian model.     

Solving Noisy ICA Using Multivariate Wavelet Denoising with an Application to Noisy Latent Variables Regression

A novel approach to solve the independent component analysis (ICA) model in the presence of noise is proposed. We use wavelets as natural denoising tools to solve the noisy ICA model. To do this, we use a multivariate wavelet denoising algorithm allowing spatial and temporal dependency. We propose also using a statistical approach, named nested design of experiments, to select the parameters such as wavelet family and thresholding type. This technique helps us to select more convenient combination of the parameters. This approach could be extended to many other problems in which one needs to choose parameters between many choices. The performance of the proposed method is illustrated on the simulated data and promising results are obtained. Also, the suggested method applied in latent variables regression in the presence of noise on real data. The good results confirm the ability of multivariate wavelet denoising to solving noisy ICA.     

On a Selection Weibull Distribution

In this article, a selection Weibull distribution is investigated. First, some properties and representations of the model with some plots of the density and hazard rate functions are illustrated. Second, some simple relations of this model with some distributions discussed. In addition, maximum likelihood estimators obtained with numerical methods, and compared by three sub-models with a data set that shows the performance of our model. Finally, a simulation study presented for all parameters.     

Evaluation of different statistical methods using SAS software: an in silico approach for analysis of real-time PCR data

Real-time polymerase chain reaction (PCR) is reliable quantitative technique in gene expression studies. The statistical analysis of real-time PCR data is quite crucial for results analysis and explanation. The statistical procedures of analyzing real-time PCR data try to determine the slope of regression line and calculate the reaction efficiency. Applications of mathematical functions have been used to calculate the target gene relative to the reference gene(s). Moreover, these statistical techniques compare C_t (threshold cycle) numbers between control and treatments group. There are many different procedures in SAS for real-time PCR data evaluation. In this study, the efficiency of calibrated model and delta delta C_t model have been statistically tested and explained. Several methods were tested to compare control with treatment means of C_t. The methods tested included t-test (parametric test), Wilcoxon test (non-parametric test) and multiple regression. Results showed that applied methods led to similar results and no significant difference was observed between results of gene expression measurement by the relative method.     

A generalized quantile regression model

A new class of probability distributions, the so-called connected double truncated gamma distribution, is introduced. We show that using this class as the error distribution of a linear model leads to a generalized quantile regression model that combines desirable properties of both least-squares and quantile regression methods: robustness to outliers and differentiable loss function.     

Fast,closed-form,and efficient estimators for hierarchical models with AR(1) covariance and unequal cluster sizes

This article is concerned with statistically and computationally efficient estimation in a hierarchical data setting with unequal cluster sizes and an AR(1) covariance structure. Maximum likelihood estimation for AR(1) requires numerical iteration when cluster sizes are unequal. A near optimal non-iterative procedure is proposed. Pseudo-likelihood and split-sample methods are used, resulting in computing weights to combine cluster size specific parameter estimates. Results show that the method is statistically nearly as efficient as maximum likelihood, but shows great savings in computation time.     

Iranian College Students’ Attitudes Toward Premarital Sex,Marriage, and Family Before and After the Islamic Revolution

ABSTRACT. Objectives: The purpose of this study was to examine Iranian college students’ attitudes toward premarital sex and marriage before and after the Islamic Revolution. Methods: Responses to a survey from 526 students at University of Shiraz in 2011 were compared to those from another study of 392 students from the same university who completed the same survey in 1977 (2 years before the Islamic Revolution). Results: No substantial changes were observed to indicate that college students adopted theocratic views on premarital sex and marriage after the Islamic Revolution. Conclusions: The Islamic regime's efforts to cultivate conservative attitudes toward sexuality and marriage have not achieved their goals.