A simulation comparison on spatial Poisson mixed models

The statistical methods for analyzing spatial count data have often been based on random fields so that a latent variable can be used to specify the spatial dependence. In this article, we introduce two frequentist approaches for estimating the parameters of model-based spatial count variables. The comparison has been carried out by a simulation study. The performance is also evaluated using a real dataset and also by the simulation study. The simulation results show that the maximum likelihood estimator appears to be with the better sampling properties.     

Order statistics and their concomitants from multivariate normal mean–variance mixture distributions with application to Swiss Markets Data

In this article, by considering a multivariate normal mean–variance mixture distribution, we derive the exact joint distribution of linear combinations of order statistics and their concomitants. From this general result, we then deduce the exact marginal and conditional distributions of order statistics and their concomitants arising from this distribution. We finally illustrate the usefulness of these results by using a Swiss markets dataset.     

Long-term effects of back extensor strengthening exercises on quality of life in women with osteoporosis

The aim of the present study was to evaluate the long-term effect of back extensor strengthening exercises on health-related quality of life (QOL) in women with osteoporosis. In this randomized clinical trial, 183 women with osteoporosis were treated with pharmacotherapy and weight-bearing and balance-training exercises. The case group additionally performed back extensor exercises at home. Patients filled out the Persian version of the Short Form (SF-36) QOL questionnaire at baseline and 6 months post treatment. At the end, all physical and mental parameters of the SF-36 questionnaire improved significantly in the case group, except for one subscale of mental health, compared to the control group. In the control group, only some physical health dimensions (bodily pain, role limitation, physical function, vitality), and mental health status as a mental health subscale improved. In conclusion, considering a major impact of back extensor exercises on improving QOL in women with osteoporosis over the long term, these exercises should be prescribed in routine management of these patients.     

Testing the difference between spectral densities of two independent periodically correlated (cyclostationary) time series models

In this work, the asymptotic distribution for the discrete Fourier transform of periodically correlated (PC) processes is applied to test the equality of two PC time series. Then the performance of the proposed method is investigated through the Monte Carlo simulations.     

Correction to: The Weibull Fréchet distribution and its applications

Afify et al. [The Weibull Fréchet distribution and its applications, J. Appl. Stat., 43 (2016), pp. 2608–2626] defined and studied a new four-parameter lifetime model called the Weibull Fréchet distribution. They made some mistakes in presenting the log-likelihood function and the components of score vector. In this note, we will correct them.     

Social Participation, Sense of Community and Social Well Being: A Study on American, Italian and Iranian University Students

Aim of the study was to assess the relationship between social participation and Sense of Community in a sample of University students and the impact of such variables on Social well being. A further aim was to assess the generality of the relationships between these constructs across different countries, and specifically, the USA, Italy and Iran. The sample includes 200 Italian, 125 American and 214 Iranian University students, male and female. Results show higher levels of social participation, Sense of Community and Social well being among American students. Sense of Community is positively correlated with social participation in all three samples; however, only among Italian students social participation positively predicts Social well being. Implications of results will be discussed.     

Gender Differences in Publication among University Professors in Canada*

Cet article analyse un important sondage à l'échelle canadienne et aborde la probématique de la productivité: pourquoi les professeures d'université publient‐elles moins que leurs collégues hommes ? Les résultats montrent que, dans l'ensemble, les femmes ont publié moins que les hommes — et ce, de manière significative —, à la fois durant leur carrière et au cours des trois années qui ont précédé le sondage. Cependant, des analyses multivariables révèlent que des différences s'avèrent plus prononcées dans les données touchant la carrière que dans celles de la courte période. La plus grande différence entre les hommes et les femmes a trait au fait de publier dans une revue à comité de lecture ou sans, et s'applique à toute leur carrière. Enfin, des différences se laissent expliquer par des différences de rang, d'années depuis l'obtention du doctorat, la discipline, le type d'université ainsi que le temps consacré a la recherche. Des problèmes d'évaluation des prédicteurs de la productivité en recherche sont discutés. This paper analyses a large Canadian national survey of professors and tackles the “productivity puzzle” as to why female scientists publish less than male scientists. Results show that, in aggregate, Canadian female professors have published significantly less than their male counterparts, both over their lifetimes and during the three years before the survey. However, multivariate analyses reveal that gender differences in publication are more pronounced in the lifetime data than in the data for the shorter period. Much of the difference in publication between men and women of the academy is in refereed and non‐refereed articles and reports over their career. Finally, gender differences in publication are largely accounted for by differences in rank, years since PhD, discipline, type of university and time set aside for research. Problems of assessing predictors of research productivity are discussed.     

Maximum likelihood estimation of sensitive proportion using repeated randomized response techniques

Randomized response techniques are designed to obtain usable data on sensitive issues while protecting the privacy of individuals. In this paper, based on repeating the randomized response technique, a new technique called repeated randomized response is introduced to increase the protection of privacy and efficiency of estimator for proportion of sensitive attribute. By using this technique, the proportion of academic cheating is estimated among students of Shahid Chamran University of Ahvaz, Ahvaz, Iran.     

The inverse 1-center problem on trees with variable edge lengths under Chebyshev norm and Hamming distance

This paper addresses the problem of modifying the edge lengths of a tree in minimum total cost such that a prespecified vertex becomes the 1-center of the perturbed tree. This problem is called the inverse 1-center problem on trees. We focus on the problem under Chebyshev norm and Hamming distance. From special properties of the objective functions, we can develop combinatorial algorithms to solve the problem. Precisely, if there does not exist any vertex coinciding with the prespecified vertex during the modification of edge lengths, the problem under Chebyshev norm or bottleneck Hamming distance is solvable in \(O(n\log n)\) time, where \(n+1\) is the number of vertices of the tree. Dropping this condition, the problem can be solved in \(O(n^{2})\) time.