Older people, work and equal opportunity

People in industrialized countries are living longer, having fewer children and retiring sooner. The proportion of older people in the population is rising; their labour force participation is declining. These trends are arousing apprehensions about future labour supply and pension financing as contributor/beneficiary ratios decrease. A widely advocated policy response is to seek higher participation rates, especially by raising pensionable ages and restricting early retirement. Little has been done to improve the labour market position of seniors. Three-pronged action is needed: promoting training, placement and workplace flexibility; changing attitudes through education and information; and prohibiting age discrimination in employment.     

Order statistics from non-identical right-truncated Lomax random variables with applications

In this paper, we derive some recurrence relations for the single and the product moments of order statistics from n independent and non-identically distributed Lomax and right-truncated Lomax random variables. These recurrence relations are simple in nature and could be used systematically in order to compute all the single and product moments of all order statistics in a simple recursive manner. The results for order statistics from the multiple-outlier model (with a slippage of p observations) are deduced as special cases. We then apply these results by examining the robustness of censored BLUE's to the presence of multiple outliers. Received: November 30, 1998; revised version: March 8, 2000     

Modeling longitudinal count data with dropouts

This paper explores the utility of different approaches for modeling longitudinal count data with dropouts arising from a clinical study for the treatment of actinic keratosis lesions on the face and balding scalp. A feature of these data is that as the disease for subjects on the active arm improves their data show larger dispersion compared with those on the vehicle, exhibiting an over‐dispersion relative to the Poisson distribution. After fitting the marginal (or population averaged) model using the generalized estimating equation (GEE), we note that inferences from such a model might be biased as dropouts are treatment related. Then, we consider using a weighted GEE (WGEE) where each subject's contribution to the analysis is weighted inversely by the subject's probability of dropout. Based on the model findings, we argue that the WGEE might not address the concerns about the impact of dropouts on the efficacy findings when dropouts are treatment related. As an alternative, we consider likelihood‐based inference where random effects are added to the model to allow for heterogeneity across subjects. Finally, we consider a transition model where, unlike the previous approaches that model the log‐link function of the mean response, we model the subject's actual lesion counts. This model is an extension of the Poisson autoregressive model of order 1, where the autoregressive parameter is taken to be a function of treatment as well as other covariates to induce different dispersions and correlations for the two treatment arms. We conclude with a discussion about model selection. Published in 2009 by John Wiley & Sons, Ltd.     

Detection of outliers in simple circular regression models using the mean circular error statistic

The investigation on the identification of outliers in linear regression models can be extended to those for circular regression case. In this paper, we propose a new numerical statistic called mean circular error to identify possible outliers in circular regression models by using a row deletion approach. Through intensive simulation studies, the cut-off points of the statistic are obtained and its power of performance investigated. It is found that the performance improves as the concentration parameter of circular residuals becomes larger or the sample size becomes smaller. As an illustration, the statistic is applied to a wind direction data set.     

Minimization of model inadequacy when observations subject to shift in means and variances

In this article optimality of experimental design for fitting a lower-order polynomial to a higher order response function for the situation in which observations may be subject to shift in means as well as in variances is considered. It is found that Karson, Manson and Hader‘s (1969) optimum designs provide pro-tection, in some sense, against model inadequacies even when observations are subject to shift in means and variances.     

Expenditure Differences of University Degree Holders Across Occupational Sectors in Malaysia

This study was motivated by the key role university degree holders play in Malaysia's vision for the future and by concerns expressed about the drift of university degree holders from one sector to another. A questionnaire was mailed to a sample of 400 Malaysian families that had at least one member who held a university degree. The objective was to elicit details of the household economic situation of respondents, with special reference to the differences in expenditure patterns between families whose degree holder worked in higher education, government, or the private sector.Results of tobit analysis of expenditures show that there are some differences between the sectors regarding expenditure patterns, but the differences are not as great as expected. Nevertheless, university-educated persons in the private sector seem to have somewhat different expenditure patterns than their counterparts in other sectors.     

Reversed preservation of stochastic orders for random minima and maxima with applications

In this paper, reversed preservation properties of right spread order, total time on test order and increasing convex (concave) order when taking random minima and maxima are developed. In this context, reversed preservation properties of some ageing concepts are investigated under parallel (series) systems which are composed of a random number of i.i.d. components. Some applications in reliability and economics are given.     

Decision-Making, Time Horizons, and Risk in the Very Long-Term Perspective

Some decisions made today have far-reaching consequences as exemplified by those concerning nuclear power and spent nuclear fuel. The investigation presented here uses a decision theoretic framework in which time horizons and the discounting of negative consequences play significant roles. The results indicated wide variations in the lengths of the planning horizons judged to be adequate not only across a number of activities, including nuclear waste management, but also across groups of subjects (e.g., engineering students, retired people, and nuclear fuel experts). The paper reports typical judgments and correlations between different variables for different groups of subjects. The differences across groups reflect potential sources of conflict, depending in part on different values and different perceptions of more or less uncertain facts. Discounting functions for negative consequences in the future were also established. A range in differences in the speed of discounting were found and illustrated. Furthermore, it was found that substantial proportions in all groups regarded negative consequences related to nuclear waste as nondiscountable. When asked about the effect of time until outcome on acceptable probability of a negative outcome, many subjects used the probability concept in an incoherent way, illustrating the great difficulty in communicating small probabilities in a long-term risk context.