Finite mixture of regression models for a stratified sample

Despite the popularity and importance, there is limited work on modelling data which come from complex survey design using finite mixture models. In this work, we explored the use of finite mixture regression models when the samples were drawn using a complex survey design. In particular, we considered modelling data collected based on stratified sampling design. We developed a new design-based inference where we integrated sampling weights in the complete-data log-likelihood function. The expectation–maximisation algorithm was developed accordingly. A simulation study was conducted to compare the new methodology with the usual finite mixture of a regression model. The comparison was done using bias-variance components of mean square error. Additionally, a simulation study was conducted to assess the ability of the Bayesian information criterion to select the optimal number of components under the proposed modelling approach. The methodology was implemented on real data with good results.     

Optimal designs for asymmetrical factorial paired comparison experiments

Three forms of a general null hypothesis Ho on the factorial parameters of a general asymmetrical factorial paired comparison experiment are considered. A class of partially balanced designscorresponding to each form of H₀ is constructed and the A,D and ioptimal design, minimizing the trace, determinant and largest eigenvalue of a defined covariance matrix of related maximumlikelihoodestimators, in that class is determined. Moreover, the optimal design in each class maximizes the noncentrality parameter λ² of the asymptotic noncentral chi-square distribution of the likelihood ratiostatistic -2 log λ for testing H_o under defined local alternatives. These results apply directly to symmetrical factorial paired comparison experiments as special casesExamples are given forillustrating applications of the developed results     

The municipal solid waste and the quality of life of collectors of recyclable materials in Juiz de Fora, Minas Gerais

The generation growing and diversified of Municipal Solid Waste is configured as an environmental problem, economic and social deterioration, especially, by application of inappropriate management of them. Faced with this urban context, the research in development presents as specific objective assessment of the quality of life of the gatherers of recyclable materials were active in the city of Juiz de Fora, in the brazilian state of Minas Gerais. In addition, the objective is, still, the recognition of the activity of sorting performed by "scavengers" in order to maximize the reduction, reuse and recycling energy and material waste daily. The proposed methodology is based on the application of the questionnaire Word Health Organization Quality of Life (WHOQOL-100), prepared by the World Health Organization, in order to value the quality of life of the gatherers of recyclable materials, involved, even in educational workshops in order to discuss and organize strategies of health care and scouting to the basement to public policies.     

Asymptotic relative efficiency of designs for factorial paired comparison experiments

A general approach for comparing designs of paired comparison experiments on the basis of the asymptotic relative efficiencies, in the Bahadur sense, of their respective likelihood ratio tests is discussed and extended to factorials. Explicit results for comparing five designs of 2^q factorial paired comparison experiments are obtained. These results indicate that some of the designs which require comparison of fewer distinct pairs of treatments than does the completely balanced design are, generally, more efficient for detecting main effects and/or certain interactions. The developments of this paper generalize the work of Littell and Boyett (1977) for comparing two designs of R x C factorial paired comparison experiments.     

Labour Policy and Determinants of Employment and Wages in a Developing Economy with Labour Shortage

Using data from a sample of 1,099 workers, this paper investigates the determinants of employment and wages for workers in the United Arab Emirates. The paper further examines the wage distribution and the decomposition of the wage gap between the public and the private sectors. Results of the study are consistent with the dual labour market theory and indicate that the labour market in the United Arab Emirates is segmented based on sectors (public versus private) and types of workers (nationals versus non‐nationals). The study concludes with a discussion of the implication of these findings for the effectiveness of labour and economic policy.     

On the wald,lagrangian multiplier and likelihood ratio tests when the information matrix is singular

Summary Modified formulas for the Wald and Lagrangian multiplier statistics are introduced and considered together with the likelihood ratio statistics for testing a typical null hypothesisH ₀ stated in terms of equality constraints. It is demonstrated, subject to known standard regularity conditions, that each of these statistics and the known Wald statistic has the asymptotic chi-square distribution with degrees of freedom equal to the number of equality constraints specified byH ₀ whether the information matrix is singular or nonsingular. The results of this paper include a generalization of the results of Sively (1959) concerning the equivalence of the Wald, Lagrange multiplier and likelihood ratio tests to the case of singular information matrices.     

Optimal design results for 2n factorial paired comparison experiments

Four general classes of partially balanced designs for 2ⁿ factorials, corresponding to four different forms of a general null hypothesis H on factorial effects, are presented. For the typical design in each class, the simplified form of the non-centrality parameter λ² of the asymptotic chi-square distribution of the likelihood ratio statistic for testing the corresponding form of H₀ is derived under defined local alternatives. Optimal designs d₁ maximizing λ² in the i-th class and minimizing the trace, determinant and largest eigenvalue of a defined covariance matrix, i =1,…,4, are determined.     

Impact of influence and skill on managerial performance

Part of Heller's contingency model of leadership and decision making [11] has been modified. The basic components of the modified part of the model are influence, skill use, job performance and job satisfaction. Data from a study of 97 British and Sudanese managers are used to test the modified model. Positive relationships have been found between the four components. The major findings of this research are that while the strength of the relationship between ‘influence and satisfaction’ on the one hand and ‘skill use and satisfaction’ on the other differs only slightly, the relationship between ‘skill use and performance’ is much stronger and much more established than the relationship between ‘influence and performance’. These results have been established in both the Sudan and Britain.