Some results on optimality in models with heteroscedastic errors from partial optimum designs

This paper studies optimum designs for linear models when the errors are heteroscedastic. Sufficient conditions are given in order to obtainD-, A- andE-optimum designs for a complete regression model from partial optimum designs for some sub-parameters. A result about optimality for a complete model from the optimality for the submodels is included. Supported by Junta de Andalucía, research group FQM244.     

A “brer rabbit” case for reverse mandated benefits

Reverse mandated benefits is a government-mandated policy that requires employees to provide their employers with benefits that workers would not provide otherwise. Of course, only those benefits would be mandated that are worth more to employers than they cost, as determined by political authorities. My case for such a policy argues that it is at least as sensible as policies mandating that employers provide benefits to their employees that would not be provided otherwise.     

Effects of Category Order on Answers in Mail and Telephone Surveys1

Abstract Past research suggests that mail surveys encourage a primacy effect, which is a tendency to choose the first answers from a list, whereas telephone surveys encourage a recency effect, a tendency to choose the last answers from a list. This paper summarizes results from 82 new experiments conducted in 12 separate surveys in seven states. Only four of 33 mail survey comparisons exhibited significant primacy effects, while five of 26 experiments in telephone surveys exhibited recency effects. In addition, only three of 23 cross-method comparisons produced a significant primacy/recency effect in the expected manner. The conclusion is that the prevalence of primacy and recency effects has been over-estimated by past research and a new theoretical approach that takes into account multiple causation is needed for examining these effects.     

Exposure Reconstruction for the TCDD-Exposed NIOSH Cohort Using a Concentration- and Age-Dependent Model of Elimination

Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations.     

Beheimatungsprozesse begleiten — ein Werkstattbericht

Supporting processes of belonging in supervision and coachingThe contemporary employee has to cope with frequent changes. Not only does he lose his familiar environment, he also has to find ways to familiarize himself with new places and to develop a fresh sense of belonging. This process can be understood and facilitated by interpreting the German concept of “Heimat“ as something we have to create ourselves. First experiences demonstrate the usefulness of this approach in coaching processes.     

Expected sample moments of concomitants of selected order statistics

In this paper, the task of determining expected values of sample moments, where the sample members have been selected based on noisy information, is considered. This task is a recurring problem in the theory of evolution strategies. Exact expressions for expected values of sums of products of concomitants of selected order statistics are derived. Then, using Edgeworth and Cornish-Fisher approximations, explicit results that depend on coefficients that can be determined numerically are obtained. While the results are exact only for normal populations, it is shown experimentally that including skewness and kurtosis in the calculations can yield greatly improved results for other distributions.     

Policies and strategies for integrating women in agriculture and rural development

Continued economic stagnation, civil unrest, rural-urban migration, and a series of natural disasters have impeded efforts in the Sudan to integrate women into the development process. Although the Four-Year (1988-1989 to 1991-92) Salvation, Recovery, and Development Programs Plan does not explicitly addresses women's issues, its emphasis on food security, appropriate technology for the agricultural sector, small-scale industries and handicrafts, balanced regional development, and the needs of the poorest 20% of the population guarantees that women will be major recipients. There remains a need, however, to increase women's participation in the development planning process and to base projects on reliable data on women's economic activities. More successful in defining women's needs have been community development projects--Western Savannah Development Corporation, Blue Nile Integrated Rural Development Project, Nuba Mountain Project, and Jebel Marra Rural Development Project--that combine income generation, social welfare, and agricultural research. It is recommended that all such large integrated rural development or agricultural projects allot funds specifically for women's activities and ensure coordination with women's organizations to avoid duplication and identify areas of greatest need. Also urged is the development of appropriate technologies that will alleviate women's double burden of poverty and household chores and address the inequitable distribution of income. Establishment of a women's bureau for women's affairs and development within the National Planning Department would facilitate project formulation and evaluation. In need of change if women in development projects in the Sudan are to be successful are laws that limit female land ownership and practices that deny women loans and credit.     

Return migration from Australia: a case study

"The study investigates the departure from Australia of former settlers who arrived during the 1980 calendar year. The 1980 settler arrival cohort [consists] of 75,167 visaed migrants.... The study has three main aims: (i) to analyse departures from Australia of the 1980 settler arrival cohort with a view to gauging the success of Australia's immigration program in retaining settlers; (ii) to examine the retention rates of settlers with respect to characteristics...including age, sex, marital status, country of last residence, and settler eligibility category; and (iii) to consider implications of the findings." Australia's present immigration policy is discussed, previous research on return migration from Australia is summarized, and a detailed analysis of the departure data is presented. "This study found that by August 1984, 12.4 per cent of non-refugee settlers who arrived in Australia during 1980 had departed permanently but that only 0.6 per cent of the 1980 refugee cohort had done so." These figures represent a decline in immigrant departure rates since the 1960s and early 1970s. Small differences in departure rates by place of birth, age, and marital status, which may have demographic consequences if sustained over time, are noted. (SUMMARY IN FRE AND SPA)