Utilizing Bayesian predictive power in clinical trial design

The Bayesian paradigm provides an ideal platform to update uncertainties and carry them over into the future in the presence of data. Bayesian predictive power (BPP) reflects our belief in the eventual success of a clinical trial to meet its goals. In this paper we derive mathematical expressions for the most common types of outcomes, to make the BPP accessible to practitioners, facilitate fast computations in adaptive trial design simulations that use interim futility monitoring, and propose an organized BPP-based phase II-to-phase III design framework.     

Decomposing primary and secondary effects: A new decomposition method

One strand of educational inequality research aims at decomposing the effect of social class origin on educational choices into primary and secondary effects. We formalize this distinction and present a new and simple method that allows empirical assessment of the relative magnitudes of primary and secondary effects. Contrary to other decomposition methods, this new method is unbiased, is more intuitive, and decomposes effects of both discrete and continuous measures of social origin. The method also provides analytically derived statistical tests and is easily calculated with standard statistical software. We give examples using the Danish Longitudinal Survey of Youth.     

Have unions impeded growing wage dispersion among young workers?

Wage inequality is examined for young males over the period 1980–1993. While wage inequality increased substantially for nonunion workers over this period, wage inequality increased only modestly for union workers. In part, this difference results from divergent trends in skill prices—returns to skill rose in the nonunion sector but contracted slightly in the union sector. In particular, returns to education increased sharply in the nonunion sector while remaining stagnant in the union sector. At least for young workers, these findings suggest that unions have been largely successful in resisting market pressures for greater wage inequality. We also uncover evidence suggesting that, as relative returns to education decline in the union sector, highly educated young workers become less likely to choose union employment. We acknowledge the helpful comments of Dek Terrell, Steve Trejo, and Carol Horton Tremblay.     

冒险成就的电信巨头

从任何一个角度看,全球无线手机通讯行业都在快速逼近危机的边缘。全世界已经有50多个国家的手机用户数量超过其实际人口数量。即使是在工业化国家中手机人均拥有率较低的美国,在用的手机数量也超过了2.7亿部（市场渗透率接近于90％）。今天,随着无线通讯市场的日益萎缩,     

Role of motives and attributes in consumer motion picture choice

The study focuses on consumer motion picture motives and choice criteria. Its purpose can be specified into the following objectives: (1) to examine the motivational basis of cinema attending. (2) to examine the predictive ability of movie motives and consumers' attribute importances in preference regressions of four types of movie, (3) to carry out a motion picture choice analysis by predicting audience membership with discriminant analysis. The data is based on a convinience sample of Finnish consumers (N = 228) attending one of the following types of movie: adventures/ thrillers, human/ social dramas, sex movies, entertainment movies.The results of a group of multivariate analyses (factor analysis, canonical correlation, preference regression, and discriminant analysis) indicate that consumers attending different types of films have distinctly separate motivation bases, as well as attribute importance profiles, underlying their movie choices. Each movie type had a specific preference structure, expressed by the regression coefficients. Finally, the discriminant analysis suggests that the general motive and attribute variables are effective also in predicting motion picture choice. On balance, the results were mutually supportive and exemplify the managerial usefulness of quantitative consumer analysis also in the case of such abstract leisure products as motion pictures.     

Soft cultures: the symbolism of cross-border organizing 1

It is not always true that the concept of culture implies a convergence on one meaning, one set of values, one pattern of behaviour. This paper develops the notion of soft culture. Cultures are soft in the sense that multiple renderings of reality are accepted and legitimized. Soft culture is studied in the context of cross-national technology development projects. Such projects are loosely structured communities, as organizational actors are separated in time and space. The paper demonstrates how symbols work among those actors. In addition to the traditional uses of symbolic categorizing, in soft culture the symbols also play an important role in attracting more networks to the action and licensing a wide variety of exploratory activities. These equivocal characteristics of symbols should be considered a strength in face of overwhelming uncertainty since they allow actors to construct multiple futures and pursue them.     

The accuracy of normal approximation in a heterogeneous panel data unit root test

Tests for unit roots in panel data have become very popular. Two attractive features of panel data unit root tests are the increased power compared to time-series tests, and the often well-behaved limiting distributions of the tests. In this paper we apply Monte Carlo simulations to investigate how well the normal approximation works for a heterogeneous panel data unit root test when there are only a few cross sections in the sample. We find that the normal approximation, which should be valid for large numbers of cross-sectional units, works well, at conventional significance levels, even when the number of cross sections is as small as two. This finding is valuable for the applied researcher since critical values will be easy to obtain and p-values will be readily available.