Optimal sample coordination using controlled selection

Sample coordination maximizes or minimizes the overlap of two or more samples selected from overlapping populations. It can be applied to designs with simultaneous or sequential selection of samples. We propose a method for sample coordination in the former case. We consider the case where units are to be selected with maximum overlap using two designs with given unit inclusion probabilities. The degree of coordination is measured by the expected sample overlap, which is bounded above by a theoretical bound, called the absolute upper bound, and which depends on the unit inclusion probabilities. If the expected overlap equals the absolute upper bound, the sample coordination is maximal. Most of the methods given in the literature consider fixed marginal sampling designs, but in many cases, the absolute upper bound is not achieved. We propose to construct optimal sampling designs for given unit inclusion probabilities in order to realize maximal coordination. Our method is based on some theoretical conditions on joint selection probability of two samples and on the controlled selection method with linear programming implementation. The method can also be applied to minimize the sample overlap.     

An exhaustive numerical assessment of alternative unconditional tests of a binary treatment effect

For testing the effectiveness of a treatment on a binary outcome, a bewildering range of methods have been proposed. How similar are all these tests? What are their theoretical strengths and weaknesses? Which are to be recommended and what is a coherent basis for deciding? In this paper, we take seven standard but imperfect tests and apply three different methods of adjustment to ensure size control: maximization (M), restricted maximization (B) and bootstrap/estimation (E). Across a wide conditions, we compute exact size and power of the 7 basic and 21 adjusted tests. We devise two new measures of size bias and intrinsic power, and employ novel graphical tools to summarise a huge set of results. Amongst the 7 basic tests, Liebermeister’s test best controls size but can still be conservative. Amongst the adjusted tests, E-tests clearly have the best power and results are very stable across different conditions.     

Tackling the problem of teenage pregnancy in looked‐after children: a peer mentoring approach

Teenage pregnancy is associated with adverse health and social outcomes, even after adjusting for prior disadvantage, and is recognized as a major public health issue. Rates of teenage pregnancy in the UK are among the highest in Europe. Interventions introduced in the past decade to address the problem, such as improved sex and relationships education in schools, have been accompanied by a fall in teenage pregnancy rates in the UK. However, this decline has not been mirrored among looked‐after children. In this paper, we discuss why this may be the case. We suggest that a system of peer mentoring, involving a young person, whose experience of life post‐care has been positive, may be an effective approach to tackling the problem of pregnancy in this group. Peer mentoring has the potential to assist young people in developing self‐esteem, confidence and in making choices regarding their education, personal development and relationships.     

An analysis of pulsation periods of long period variable stars

Summary.  We report the results of a period change analysis of time series observations for 378 pulsating variable stars. The null hypothesis of no trend in expected periods is tested for each of the stars. The tests are non-parametric in that potential trends are estimated by local linear smoothers. Our testing methodology has some novel features. First, the null distribution of a test statistic is defined to be the distribution that results in repeated sampling from a population of stars. This distribution is estimated by means of a bootstrap algorithm that resamples from the collection of 378 stars. Bootstrapping in this way obviates the problem that the conditional sampling distribution of a statistic, given a particular star, may depend on unknown parameters of that star. Another novel feature of our test statistics is that one-sided cross-validation is used to choose the smoothing parameters of the local linear estimators on which they are based. It is shown that doing so results in tests that are tremendously more powerful than analogous tests that are based on the usual version of cross-validation. The positive false discovery rate method of Storey is used to account for the fact that we simultaneously test 378 hypotheses. We ultimately find that 56 of the 378 stars have changes in mean pulsation period that are significant when controlling the positive false discovery rate at the 5% level.     

Electronic Markets for Truckload Transportation

A wide variety of electronic marketplace formats are used in the Truckload (TL) transportation industry, including combinatorial auctions, private and public exchanges, and electronic catalogs. Combinatorial multi‐attribute auctions are commonly used strategically to populate electronic catalogs, commonly called “routing guides,” with pricing, assignments, and priority logic. Private and public exchanges are used to complement the electronic catalogs in cases where the catalog fails. This paper discusses the TL transportation market, places the procurement of services in the context of electronic marketplace formats, and illustrates how these are currently used.     

Recent Developments in Greek Industrial Relations: Statutory and Attitudinal Changes Towards Participation and Cooperation

ABSTRACT: Industrial relations in Greece were characterised in the past by labour-management mistrust and conflict, as well as by strong government intervention which invariably influenced the state of industrial relations. Political instability and other serious interruptions, such as World War II, the enemy occupation, civil war and two military dictatorships, made any effort for improvement very difficult, if not impossible, in the 1936-1974 period. Some concerted efforts were made later and especially in the 1980s (with EEC influence and support), which met with considerable success. A series of parliamentary acts and ministerial decrees, restored trade union freedoms, introduced statutory consultation and participation, strengthened collective bargaining, and established an independent agency for the settlement of disputes. Some degree of unity was also achieved among the major political factions represented in the trade union movement. More importantly (and in spite of their traditional reluctance to cooperate) the social partners represented on the employers‘ side by the Association of Greek Industries (SEV), and on the workers‘ side by the Greek General Confederation of Labour (GSEE) are beginning to move towards the development of innovatory systems of cooperation for the solution of problems of mutual concern. Furthermore, there are also some significant structural developments, including the establishment of a growing number of enterprise-level trade unions, which are engaged in contract negotiations and agreements, and participation at the enterprise level. Additionally, appropriate research and training on both sides are helping to meet the socio-economic challenges of the current decade and beyond.