Embedding latent class regression and latent class distal outcome models into cluster-weighted latent class analysis: a detailed simulation experiment

Usually in latent class (LC) analysis, external predictors are taken to be cluster conditional probability predictors (LC models with external predictors), and/or score conditional probability predictors (LC regression models). In such cases, their distribution is not of interest. Class-specific distribution is of interest in the distal outcome model, when the distribution of the external variables is assumed to depend on LC membership. In this paper, we consider a more general formulation, that embeds both the LC regression and the distal outcome models, as is typically done in cluster-weighted modelling. This allows us to investigate (1) whether the distribution of the external variables differs across classes, (2) whether there are significant direct effects of the external variables on the indicators, by modelling jointly the relationship between the external and the latent variables. We show the advantages of the proposed modelling approach through a set of artificial examples, an extensive simulation study and an empirical application about psychological contracts among employees and employers in Belgium and the Netherlands.     

Commercial sex between men: A prospective diary‐based study

This paper describes the results of a self‐reporting dairy completed by 186 male sex workers (MSWs) over a 2‐week period in Brisbane, Sydney, and Melbourne, Australia. The diary was completed following each commercial sex encounter by the MSW. The results reveal that MSWs reported 2088 commercial sex encounters during the study period, with an average of 11.2 encounters per MSW. The majority of sex encounters took place in either the client's or the MSW's residence, with significant variations by city. The average sexual encounter lasted 70 minutes, and comprised two sexual acts, masturbation and oral sex. Condom use was reported in 67.4% of all the encounters. Using the AIDS Council safe‐sex classification system, the majority of the commercial sex encounters fell in the “safer sex” category; however, there were significant differences by source of clients and place of the encounter. Use of drugs and alcohol reveal interesting patterns: Clients were more likely to use alcohol, while MSWs had significant differences of usage of the different drugs. This study demonstrates that the majority of MSWs are offering and practicing safe sex behaviours, however, MSWs working in the street setting are still likely to be practising unsafe sex. Male sex work is becoming an organised business and this provides opportunities to implement further public health interventions.     

Portmanteau tests for linearity of stationary time series

This article considers the problem of testing for linearity of stationary time series. Portmanteau tests are discussed which are based on generalized correlations of residuals from a linear model (that is, autocorrelations and cross-correlations of different powers of the residuals). The finite-sample properties of the tests are assessed by means of Monte Carlo experiments. The tests are applied to 100 time series of stock returns.     

Caloric restriction minimizes aging effects on the femoral medial condyle

This study aimed to analyze the effects of caloric restriction on aged femoral articular cartilage of Wistar rats. Three groups of eight animals each were considered: young (YC) and old (OC) control groups fed with a normal diet and old caloric restriction group (OCR) composed of 18-month-old animals fed with a 31% less caloric diet from 6-months of age. Articular cartilage was studied through morphometry and immunohistochemistry. Body mass was 12% less in the OCR group than in the OC group. The articular cartilage from OC rats show thinner medial condyles, fewer chondrocytes, smaller chondrocytes nuclear volume and, in both condyles, a predominance of collagen type II and less collagen density compared to both YC and OCR groups (p?p?相似文献   

Practice supervisors’ perceptions of social work students and their placements – an exploratory study in the Norwegian context

Practice placement has been a basic component in Social Work Programmes for many decades in Norway as elsewhere, and supervision of students has been a valued role for social workers. Here, we have carried out a pilot study of nine supervisors from various practice settings, dealing with their experience with and views about supervision of students. The aim was to get more knowledge of student supervision today and the meaning of student supervision in different practice settings. We found that the content of supervision depended on the agency context. Supervision embodies core agency values. There was a lack of common ground between supervisors and the school of social work, and between supervisors and the students.     

Variability explained by covariates in linear mixed‐effect models for longitudinal data

Variability explained by covariates or explained variance is a well‐known concept in assessing the importance of covariates for dependent outcomes. In this paper we study R² statistics of explained variance pertinent to longitudinal data under linear mixed‐effect models, where the R² statistics are computed at two different levels to measure, respectively, within‐ and between‐subject variabilities explained by the covariates. By deriving the limits of R² statistics, we find that the interpretation of explained variance for the existing R² statistics is clear only in the case where the covariance matrix of the outcome vector is compound symmetric. Two new R² statistics are proposed to address the effect of time‐dependent covariate means. In the general case where the outcome covariance matrix is not compound symmetric, we introduce the concept of compound symmetry projection and use it to define level‐one and level‐two R² statistics. Numerical results are provided to support the theoretical findings and demonstrate the performance of the R² statistics. The Canadian Journal of Statistics 38: 352–368; 2010 © 2010 Statistical Society of Canada     

GMM in linear regression for longitudinal data with multiple covariates measured with error

Griliches and Hausman 5 Griliches, Z. and Hausman, J. A. 1986. Errors in variables in panel data. J. Econometrics, 32: 93–118. [Crossref], [Web of Science ®] [Google Scholar] and Wansbeek 11 Wansbeek, T. J. 2001. GMM estimation in panel data models with measurement error. J. Econometrics, 104: 259–268. [Crossref], [Web of Science ®] [Google Scholar] proposed using the generalized method of moments (GMM) to obtain consistent estimators in linear regression models for longitudinal data with measurement error in one covariate, without requiring additional validation or replicate data. For usefulness of this methodology, we must extend it to the more realistic situation where more than one covariate are measured with error. Such an extension is not straightforward, since measurement errors across different covariates may be correlated. By a careful construction of the measurement error correlation structure, we are able to extend Wansbeek's GMM and show that the extended Griliches and Hausman's GMM is equivalent to the extended Wansbeek's GMM. For illustration, we apply the extended GMM to data from two medical studies, and compare it with the naive method and the method assuming only one covariate having measurement error.     

‘Family money’ and ‘business money’: bankrupt entrepreneurs in a ‘question situation’

This paper addresses the question of bankruptcy and honesty in local contexts, and especially the problem of the bankrupt small businessman in conveying ‘honesty’ to the local community. Studying bankrupt entrepreneurs, the analysis explores a tacit dialogue between the failed businessmen and the small town communities where they live and work. The bankrupts respond to their seemingly mistrustful surroundings by demonstrating their respect for the dividing line between two social categories of money: ‘company money’ and ‘family money’. This discursive resource expresses business ethics and respectability, both essential for the bankrupt entrepreneur to start another business in the local community. The empirical material in the study consists of interviews with 22 businessmen who had created small businesses and experienced at least one bankruptcy, half of them in small towns. The entrepreneurs were found through court records and word of mouth. Interviews were conducted by the author and by graduate students from the Department of Sociology in Lund. All interviews were tape-recorded and transcribed verbatim.     

The determinants of worry over chronic health condition for rural couples

This study investigates the determinants of chronic health conditions that worry the member of rural couples who serves as the household financial manager. A sample of 1,115 rural couples from the NC-182 regional research project Family Resource Utilization as a Factor in Determining Economic Well-Being of Rural Families is used. The logit analysis finds that the probability of having a condition that worries the financial manager increases if she or he is middle aged or older, is not employed, and has external Locus of Control. This probability also increases when the dissatisfaction with the resources available to handle a financial emergency increases and the more often the financial manager does not have money to pay for the doctor.Preparation of this research was supported in part by the Minnesota Agricultural Experiment Station project 52–056 and the Minnesota Extension Service. Data were collected in conjunction with the cooperative regional research project NC-182, Family Resource Utilization as a Factor in Determining Economic Well-Being of Rural Families. Cooperating states are Arizona, California, Illinois, Indiana, Iowa, Kansas, Michigan, and Minnesota.Her current research interests include the economic well-being of various family forms. She received her Ph.D. from University of Illinois.Her current research interests include family financial management and consumer bankruptcy. She received her Ph.D. from the University of Missouri.Her current research interests include issues concerned with family stress management including financial stress. She received her Ph.D. at Michigan State University.Her current research interests include economic and environmental well-being for families and individuals with emphasis on the impact of environmental regulations on economic well-being. She received her Ph.D. from University of Illinois.His current interests include economic well-being of rural families. He was a research assistant for Dr. Bauer before receiving his Ph.D. degree in Agriculture and Applied Economics, University of Minnesota, St. Paul, MN.     

Completeness of India's sample registration system: an assessment using the general growth balance method

In the preceding issue of this journal, a generalized version of the Brass growth balance method was proposed that made it applicable to populations that are not stable and are open to migration. In this companion paper, the results of applying this new procedure to data from India's Sample Registration system for the decades 1971-80 and 1981-90 are discussed. The results at the national level show that, during the decade 1981-90, 5 percent of the deaths among men, 12 percent of the deaths among women, and about 7 percent of births were being missed by the system. Further, it is estimated that the level of under-enumeration in the 1991 Census was more than that of the 1981 Census by 0.7 percent for males and 1.4 percent for females. The paper also presents results for major Indian states.