Bias of maximum likelihood estimators of the response standard deviation in regression

The bias of maximum likelihood estimators of the standard deviation of the response in location/scale regression models is considered. Results are obtained for a very wide family of densities for the response variable. These are used to propose point estimators with improved mean square error properties and to demonstrate the importance of bias correction in statistical inference when samples are moderately small.     

A monte carlo study of variable selection and inferences in a two stage random coefficient linear regression model with unbalanced data

A growth curve analysis is often applied to estimate patterns of changes in a given characteristic of different individuals. It is also used to find out if the variations in the growth rates among individuals are due to effects of certain covariates. In this paper, a random coefficient linear regression model, as a special case of the growth curve analysis, is generalized to accommodate the situation where the set of influential covariates is not known a priori. Two different approaches for seleaing influential covariates (a weighted stepwise selection procedure and a modified version of Rao and Wu’s selection criterion) for the random slope coefficient of a linear regression model with unbalanced data are proposed. Performances of these methods are evaluated by means of Monte-Carlo simulation. In addition, several methods (Maximum Likelihood, Restricted Maximum Likelihood, Pseudo Maximum Likelihood and Method of Moments) for estimating the parameters of the selected model are compared Proposed variable selection schemes and estimators are appliedtotheactualindustrial problem which motivated this investigation.     

Young Malinowski

Roy Ellen, Ernest Gellner, Grazyna Kubica, Janusz Mucha (eds). Malinowski between two worlds: the Polish roots of an anthropological tradition. Cambridge: Cambridge University Press. 1988. xxv, 261pp., illustrations, appendices, bibliography, index. $85.00 (hardback) ISBN 0 521 34566 9.

Robert J. Thornton and Peter Skalnik (eds). The early writings of Bronislaw Malinowski (trans. Ludwik Krzyzanowski). Cambridge: Cambridge University Press. 1993. xv, 324pp., notes, bibliography, index. $120.00 (hardback) ISBN 0521 38300 5.

Daniel Gerould (ed. and trans.). The Witkiewicz reader. Evanston, Illinois: Northwestern University Press. 1992. xiii, 359pp. illustrations, appendix, biographical notes, select bibliography. US$59.95 (hardback) ISBN 0 8101 0980 8; US$22.50 (paper) ISBN 0 8101 0994 8.     

Index for Volume 32

Abstract

College students with insulin-dependent diabetes mellitus often ignore the care of their illness. Faced with managing this illness independently for the first time, they lack the knowledge and experience to do so effectively. Their need to establish autonomy often prevents them from seeking the advice of health professionals. In view of this, the author undertook a pilot study to investigate the role of a peer support group on a college campus as a means of improving the diabetic students' management of their illness.

Three closed-membership groups met for 10 weekly sessions. Hemoglobin A_1c (the measure of average blood sugar over the preceding 3-month interval) determinations prior to participation in the group ranged from 4.0 to 11.7, with a mean of 8.16; after participation in the group, the mean hemoglobin A_1c levels of group members dropped to 6.10 (p < .001). (Hemoglobin A_1c measures lower than 6.2 reflect physiologic blood sugar measures of someone without diabetes.)

These results suggest that the peer-group approach may be a viable way to improve the metabolic control of young adults with diabetes at the time in their lives when they are learning to manage their illness independently.     

‘Mobile mindsets’: EGM venue usage,gambling participation,and problem gambling among three itinerant groups on the Sunshine Coast of Australia

Mobile populations form an increasingly important part of many communities, yet tend to be neglected by problem gambling prevalence research. We explore relationships between problem gambling and the ways in which mobile subgroups use gambling venues. Adopting a combination of quantitative and qualitative techniques, we conduct an exploratory examination of three subgroups – construction workers, ‘grey nomads’, and ‘southerner’ tourists on the Sunshine Coast of Queensland, Australia. The groups displayed substantial differences in venue visitation, gambling behaviour and problem gambling risk. The group with the least discretionary mobility, the construction workers, were most heavily dependent on gambling venues for economic and social relationships. This translated into higher levels of problem gambling risk, which was further mediated by the inter-personal connectedness of individuals. These results suggest that mobility per se does not directly result in higher risk of problem gambling but combines with social isolation to place individuals at risk.