A correlation type procedure for assessing multivariate normality

A correlation-type statistic for assessing multivariate normality is described. Its estimated finite sample distribution is tabulated, and its performance against certain alternatives is compared with that of a competing Cramer-von Mises type statistic in a Monte Carlo power study. A set of quadrivariate data is examined as illustration of the procedure.     

Book review

W.G.Cochran: Sampling Techniques, 3rd. Ed. John Wiley & Sons, New York-Santa Barbara-London-Sydney-Toronto 1977. 428 S., £ 12.50; $21.50.

H.Toutenburg: Vorhersage in linearen Modellen. Akademie-Verlag, Berlin 1975, VIII, 176b S., 3 Tab., 28,– M.

O.Kallenberg: Random Measure. Akademie-Verlag, Berlin 1975; Academic Press, London 1976. 104 pp., 28,– M.     

Simulation of the p-generalized Gaussian distribution

In this paper, we introduce the p-generalized polar methods for the simulation of the p-generalized Gaussian distribution. On the basis of geometric measure representations, the well-known Box–Muller method and the Marsaglia–Bray rejecting polar method for the simulation of the Gaussian distribution are generalized to simulate the p-generalized Gaussian distribution, which fits much more flexibly to data than the Gaussian distribution and has already been applied in various fields of modern sciences. To prove the correctness of the p-generalized polar methods, we give stochastic representations, and to demonstrate their adequacy, we perform a comparison of six simulation techniques w.r.t. the goodness of fit and the complexity. The competing methods include adapted general methods and another special method. Furthermore, we prove stochastic representations for all the adapted methods.     

Comparison of performance measures for multivariate discrete models

For multivariate probit models, Spiess and Tutz suggest three alternative performance measures, which are all based on the decomposition of the variation. The multivariate probit model can be seen as a special case of the discrete copula model. This paper proposes some new measures based on the value of the likelihood function and the prediction-realization table. In addition, it generalizes the measures from Spiess and Tutz for the discrete copula model. Results of a simulation study designed to compare the different measures in various situations are presented.     

Testing lack of fit of regression models under heteroscedasticity

A test is proposed for assessing the lack of fit of heteroscedastic nonlinear regression models that is based on comparison of nonparametric kernel and parametric fits. A data-driven method is proposed for bandwidth selection using the asymptotically optimal bandwidth of the parametric null model which leads to a test that has a limiting normal distribution under the null hypothesis and is consistent against any fixed alternative. The resulting test is applied to the problem of testing the lack of fit of a generalized linear model.     

Tests of symmetry based on transformed empirical processes

A probability distribution function F is said to be symmetric when 1 ‐ F(x) ‐ F(‐x) = 0 for all x∈ R. Given a sequence of alternatives contiguous to a certain symmetric F₀, the authors are concerned with testing for the null hypothesis of symmetry. The proposed tests are consistent against any nonsymmetric alternative, and their power with respect to the given sequence can easily be optimized. The tests are constructed by means of transformed empirical processes with an adequate selection of the underlying isometry, and the optimum power is obtained by suitably choosing the score functions. The test statistics are very easy to compute and their asymptotic distributions are simple.     

Correlated random effects regression analysis for a log-normally distributed variable

In regression analysis, it is assumed that the response (or dependent variable) distribution is Normal, and errors are homoscedastic and uncorrelated. However, in practice, these assumptions are rarely satisfied by a real data set. To stabilize the heteroscedastic response variance, generally, log-transformation is suggested. Consequently, the response variable distribution approaches nearer to the Normal distribution. As a result, the model fit of the data is improved. Practically, a proper (seems to be suitable) transformation may not always stabilize the variance, and the response distribution may not reduce to Normal distribution. The present article assumes that the response distribution is log-normal with compound autocorrelated errors. Under these situations, estimation and testing of hypotheses regarding regression parameters have been derived. From a set of reduced data, we have derived the best linear unbiased estimators of all the regression coefficients, except the intercept which is often unimportant in practice. Unknown correlation parameters have been estimated. In this connection, we have derived a test rule for testing any set of linear hypotheses of the unknown regression coefficients. In addition, we have developed the confidence ellipsoids of a set of estimable functions of regression coefficients. For the fitted regression equation, an index of fit has been proposed. A simulated study illustrates the results derived in this report.     

Working and caring for a disabled adopted child during a pandemic

Integrating work and family demands can be challenging for families caring for a child with one or more disabilities. The pandemic and its changes to work, schooling and service delivery potentially added to these challenges. This exploratory mixed methods study sought to understand how the pandemic affected adoptive parents' work–life fit and service use. A total of 200 participants responded to survey questions about parenting an adopted child with a disability prior to, and after, the onset of Covid-19. More than half of the parents (59.2%) reported that it was somewhat to very difficult to integrate both work and family demands. Parents with greater access to workplace flexibility and supportive supervisors had significantly less difficulties combining work and family. Families who reported more problems with accessing mental health services, special education and respite care reported significantly more challenges with work–family fit. Parents reported increased stress due to the pandemic changes, but many also shared positive changes such as more time for family. Online services were experienced as effective for some children and reduced time spent driving to appointments. Recommendations for workplace and social service practice and policy supporting adoptive parents of children with disabilities are discussed.     

The future of PR is ‘fantastic’, ‘friendly’ and ‘funny’: Occupational stereotypes and symbolic capital in entry-level job advertisements

Over the past decade, there has been a move towards examining public relations as a socio-cultural practice, acknowledging practitioners as influential communicators who produce and symbolise cultural values through public relations messages. Ideally, a diverse group of professionals would aide in representing a diverse society, but to date, the profession remains female dominated. In this article, it is proposed that practitioners’ own discourse do not only establish what is most valued in the occupation and which habitus suits the practice best, but that the discourse also opens and closes occupational entry for new practitioners thereby contributing to a lack of diversity.This article presents the findings of an indicative thematic content analysis of one of the most common, yet under-research sites of discourse, namely entry-level job advertisements in New Zealand and Australia. Using an interdisciplinary approach, the analysis found that the advertisements placed little to no emphasis on the nature of the work, instead focusing on elements of ‘fit’ whereby new entrants were expected to be charismatic, friendly, and willing to work in an environment that is ‘fun’ and ‘flexible’. In doing so, public relations practitioners tacitly created invisible barriers, a self-limiting occupational culture and furthered existing stereotypes of the ‘perfect’ practitioner.