Optimal orthogonal-array-based latin hypercubes

The use of optimal orthogonal array latin hypercube designs is proposed. Orthogonal arrays were proposed for constructing latin hypercube designs by Tang (1993). Such designs generally have better space filling properties than random latin hypercube designs. Even so, these designs do not necessarily fill the space particularly well. As a result, we consider orthogonal-array-based latin hypercube designs that try to achieve optimality in some sense. Optimization is performed by adapting strategies found in Morris & Mitchell (1995) and Ye et al. (2000). The strategies here search only orthogonal-array-based latin hypercube designs and, as a result, optimal designs are found in a more efficient fashion. The designs found are in general agreement with existing optimal designs reported elsewhere.     

100 key research questions for the post‐2015 development agenda

The Sustainable Development Goals (SDGs) herald a new phase for international development. This article presents the results of a consultative exercise to collaboratively identify 100 research questions of critical importance for the post‐2015 international development agenda. The final shortlist is grouped into nine thematic areas and was selected by 21 representatives of international and non‐governmental organisations and consultancies, and 14 academics with diverse disciplinary expertise from an initial pool of 704 questions submitted by 110 organisations based in 34 countries. The shortlist includes questions addressing long‐standing problems, new challenges and broader issues related to development policies, practices and institutions. Collectively, these questions are relevant for future development‐related research priorities of governmental and non‐governmental organisations worldwide and could act as focal points for transdisciplinary research collaborations.     

Tests of symmetry with one-sided alternatives in three-way contingency tables

For a two-dimensional contingency table of probabilities, the concept of symmetry around the main diagonal is well defined. Statistical hypothesis test of symmetry versus positive bias have also been explored. For tables of higher (three or more) dimensions, however, different concepts of symmetry are available. In this study, we consider statistical inference procedures of symmetry in partial tables versus various biases in three-dimensional tables. We find the maximum likelihood estimates of the cell probabilities and the asymptotic distribution of the likelihood ratio test statistic in each case. Simulation studies are used to investigate the sizes and powers of the tests. The methodologies developed are applied on real data sets.     

Testing for ordered failure rates under general progressive censoring

For exponentially distributed failure times under general progressive censoring schemes, testing procedures for ordered failure rates are proposed using the likelihood ratio principle. Constrained maximum likelihood estimators of the failure rates are found. The asymptotic distributions of the test statistics are shown to be mixtures of chi-square distributions. When testing the equality of the failure rates, a simulation study shows that the proposed test with restricted alternative has improved power over the usual chi-square statistic with an unrestricted alternative. The proposed methods are illustrated using data of survival times of patients with squamous carcinoma of the oropharynx.     

Multi-phase Algorithms for Throughput Maximization for Real-Time Scheduling

We consider the problem of off-line throughput maximization for job scheduling on one or more machines, where each job has a release time, a deadline and a profit. Most of the versions of the problem discussed here were already treated by Bar-Noy et al. (Proc. 31st ACM STOC, 1999, pp. 622–631; http://www.eng.tau.ac.il/amotz/). Our main contribution is to provide algorithms that do not use linear programming, are simple and much faster than the corresponding ones proposed in Bar-Noy et al. (ibid., 1999), while either having the same quality of approximation or improving it. More precisely, compared to the results of in Bar-Noy et al. (ibid., 1999), our pseudo-polynomial algorithm for multiple unrelated machines and all of our strongly-polynomial algorithms have better performance ratios, all of our algorithms run much faster, are combinatorial in nature and avoid linear programming. Finally, we show that algorithms with better performance ratios than 2 are possible if the stretch factors of the jobs are bounded; a straightforward consequence of this result is an improvement of the ratio of an optimal solution of the integer programming formulation of the JISP2 problem (see Spieksma, Journal of Scheduling, vol. 2, pp. 215–227, 1999) to its linear programming relaxation.     

The consumer expenditures of elderly women: Racial,marital, and rural/urban impacts

This research, using data from the interview component of the 1990 Consumer Expenditure Survey (CES), examines the main and interaction effects of race, marital status, and residence on the economic well-being of women 65 years or older (N=3,205). Economic well-being is measured by total annualized expenditures of the household for goods and services. The first hypothesis is supported: race, marital status, and urban or rural residence each has a major effect on the economic well-being of older women after adjusting for the effects of age and household size. The characteristics of nonwhite, nonmarried, and rural are associated with lower economic well-being. The second hypothesis is not supported: race, marital status, and residence do not interact to produce differences in the economic well-being of older women. Both hypotheses are examined by analysis of covariance. The results show the economic diversity of older women and the persistent effects of race, marital status, and rural or urban residence on the economic well-being of older women regardless of age and household size. This research was conducted at the Agricultural Research Service, United States Department of Agriculture (Family Economics Research Group), Hyattsville, MD, July 1992, where Dr. Kivett was a Visiting Scientist at the time. Appreciation is expressed to the staff of the Family Economics Research Group for their technical assistance at all stages of the research. and 1992 Visiting Professor at the Family Economics Research Group, Agricultural Research Service, U.S. Department of Agriculture. Her current research interests include the family supports and relationships of older retired migrants. She received her Ph.D. from the University of North Carolina at Greensboro. Her current research interests include the economic status of elderly American households. She received her Ph.D. from the University of Maryland.     

Kin Expectations and Kin Support Among Rural Older Adults1

Abstract Relatively little attention has been given to the kin ties of rural older adults. To partially fill this gap in knowledge, kin selection theory was used as a conceptual framework to explore two questions on the extent rural older adults expect and receive assistance from the range of affinal and consanquineal kin and the factors that best explain the current level of support provided by each of the kin types in the family system. Analysis was based on interviews conducted in 1985–1986 with 368 rural older adults in the Piedmont region of North Carolina. Expectations of kin assistance were much higher than the actual level of support that was provided. Both expected and actual levels of assistance declined as the level of consanguineous kin and associated affinal ties decreased. The level of support provided by kin groups was mainly a function of geographic distance to kin and norms of obligation.     

Probabilistic cheap talk

We consider a model in which there is uncertainty over when a one-shot game will be played. We show how a mechanism designer can implement desirable outcomes in certain economic games by manipulating only the probability that the game is played in a given round while leaving all other aspects of the game unchanged. We also show that if there is no discounting, this uncertainty imparts a sequential structure that is almost mathematically equivalent to a repeated version of the game with discounting. In particular, a folk theorem applies to such games. Thus, games of probabilistic cheap provide a third interpretation of the repeated game framework with the additional feature that expected payoff is invariant to the probability of the game ending. Received: 10 May 1999/Accepted: 16 October 2000