Random Weighted Bootstrap Method for Recurrent Events with Informative Censoring

Using the data from the AIDS Link to Intravenous Experiences cohort study as an example, an informative censoring model was used to characterize the repeated hospitalization process of a group of patients. Under the informative censoring assumption, the estimators of the baseline rate function and the regression parameters were shown to be related to a latent variable. Hence, it becomes impractical to directly estimate the unknown quantities in the moments of the estimators for the bandwidth selection of a smoothing estimator and the construction of confidence intervals, which are respectively based on the asymptotic mean squared errors and the asymptotic distributions of the estimators. To overcome these difficulties, we develop a random weighted bootstrap procedure to select appropriate bandwidths and to construct approximated confidence intervals. One can see that our method is simple and faster to implement from a practical point of view, and is at least as accurate as other bootstrap methods. In this article, it is shown that the proposed method is useful through the performance of a Monte Carlo simulation. An application of our procedure is also illustrated by a recurrent event sample of intravenous drug users for inpatient cares over time.     

The Conceptual Contours of Sex in the Chinese Life Sciences: Zhu Xi (1899–1962), Hermaphroditism, and the Biological Discourse of Ci and Xiong, 1920–1950

This paper “maps” a number of trajectories through which the conceptual contours of sex could be traced in the bioscientific discourse of Republican China. Focusing on the writings of the embryologist Zhu Xi (1899–1962), I analyze the epistemic functionality of such biological terms as ci (“biological femaleness”) and xiong (“biological maleness”) that acquired an unprecedented scope of cultural discursiveness in China only alongside the arrival of Western biology, which replaced classical learning and natural studies as the authoritative field of inquiry about life. I first show that when Chinese scientists used these terms to describe the sex of biological species, they relied on an epistemological framework of visual knowledge that granted some foundational operative power to a signifying order in which one could know by seeing the differences between ci and xiong (and, ultimately, sexual differences). These two terms’ lexicality and indexicality thus mutually reinforced one another in the production of their semiotic possibilities and epistemo-logicality. I then show that while they adopted ci and xiong as the bioscientific synonyms of the more culturally anthropocentric words such as nü (woman) and nan (man), Chinese biologists also incorporated sophisticated biological theories of sex from Europe and North America, including the theories of “gynandromorphism” and “intersexuality.” The implicit and explicit figurations of hermaphroditism reveal the ways in which at the heart of the entire bioscientific discourse of ci and xiong resides its key conceptual anchor: the human–non-human divide.

Predicting project approvals: A case of grants from the National Science Council of Taiwan

Project selection is an important task for organizations in achieving their missions using limited budgets and resources. Whether or not a project will be approved is also of primary concern to the applicants. This paper predicts whether a project will be approved for cases where the criteria for evaluating it are known while the scoring system is not. The idea is to construct a frontier function for the approved projects from past performance on the criteria. The relative distance between a proposed project and the frontier serves as an indicator of the possibility that the project will be approved. Data from the Management II Division of the National Science Council of Taiwan in the Topic Research Project are collected to illustrate this approach. From the percentile of the distance measure, an applicant is able to predict the possibility that their project will be approved. Since professors with different levels of experience and different research areas have different research performance, these factors are taken into account in the prediction. A Malmquist productivity index analysis is also conducted to investigate the performance improvement of the applicants in research between two periods.     

Judgment of distributional inequality in networks

Why is income inequality perceived and judged differently across a society? Following the social comparison theory, one reasonable explanation suggests that individuals are exposed to different local reference groups in social networks. We design a vignette experiment to study how income distributions are judged by individuals structured in networks. The experiment shows that perceptions of distributional inequality are high when network ties are unequally distributed across individuals, suggesting that network inequality contributes to distributional inequality. Beyond the network effect, inequality judgment is found to be driven by a mix of self-interest and other-regarding preference: people are in favor of group-beneficial income distributions wherein they rank high, but not extremely high, in the group. It shows that people care about not only their relative affluence, but also where others stand in the distribution.     

Some results on the target set selection problem

In this paper we consider a fundamental problem in the area of viral marketing, called Target Set Selection problem. We study the problem when the underlying graph is a block-cactus graph, a chordal graph or a Hamming graph. We show that if G is a block-cactus graph, then the Target Set Selection problem can be solved in linear time, which generalizes Chen’s result (Discrete Math. 23:1400–1415, 2009) for trees, and the time complexity is much better than the algorithm in Ben-Zwi et al. (Discrete Optim., 2010) (for bounded treewidth graphs) when restricted to block-cactus graphs. We show that if the underlying graph G is a chordal graph with thresholds θ(v)≤2 for each vertex v in G, then the problem can be solved in linear time. For a Hamming graph G having thresholds θ(v)=2 for each vertex v of G, we precisely determine an optimal target set S for (G,θ). These results partially answer an open problem raised by Dreyer and Roberts (Discrete Appl. Math. 157:1615–1627, 2009).     

Promotions and the pattern of grocery shopping time

The histograms of interpurchase times for frequently purchased packaged goods have consistently shown pronounced seven-day cycles. Evidence supports that the weekly spike phenomenon is the result of consumers' regular shopping trip schedules. We explore the implications of this peculiar regularity on the issue of consumer purchase timing acceleration. Data for five product categories are examined. Promotions are found to have little effect in accelerating purchase timing. In contrast, conventional interpurchase time models are shown to overstate the effect of promotions.     

A fuzzy AHP application in government-sponsored R&D project selection

Due to the funding scale and complexity of technology, the selection of government sponsored technology development projects can be viewed as a multiple-attribute decision that is normally made by a review committee with experts from academia, industry, and the government. In this paper, we present a fuzzy analytic hierarchy process method and utilize crisp judgment matrix to evaluate subjective expert judgments made by the technical committee of the Industrial Technology Development Program in Taiwan. Our results indicate that the scientific and technological merit is the most important evaluation criterion considered in overall technical committees. We demonstrate how the relative importance of the evaluation criteria changes under various risk environments via simulation.     

The relationship between information content and institutional investors: evidence from new product preannouncements

In this study, we investigate the relationship between information content of new product preannouncements (NPPAs) and trading behaviors of institutional investors. Using hand-collected data from 1995 to 2004, in empirical results, we find that there is a significantly positive relationship between information content and institutional investors. NPPAs can help institutional investors to evaluate the potential success of forthcoming new products through signaling enough information content. As a result, more information cues and earlier NPPAs can make institutional investors choose these preannouncing firms into their investment portfolios to increase their holdings and attract more different institutional investors to hold these shares of preannouncing firms. In addition, we also find the positive advertising and R&D investment effects. Our findings suggest that managers should use the information content of NPPA signals to reduce information asymmetry and help managers to implement their NPPA strategies so as to receive greater financial support from institutional investors.     

Symmetric quantiles and their applications

To develop estimators with stronger efficiencies than the trimmed means which use the empirical quantile, Kim (1992) Kim, S. J. 1992. The metrically trimmed means as a robust estimator of location. Annals of Statistics, 20: 1534–1547. [Crossref], [Web of Science ®] [Google Scholar] and Chen & Chiang (1996) Chen, L. A. and Chiang, Y. C. 1996. Symmetric type quantile and trimmed means for location and linear regression model. Journal of Nonparametric Statistics, 7: 171–185. [Taylor & Francis Online] [Google Scholar], implicitly or explicitly used the symmetric quantile, and thus introduced new trimmed means for location and linear regression models, respectively. This study further investigates the properties of the symmetric quantile and extends its application in several aspects. (a) The symmetric quantile is more efficient than the empirical quantiles in asymptotic variances when quantile percentage α is either small or large. This reveals that for any proposal involving the α th quantile of small or large α s, the symmetric quantile is the right choice; (b) a trimmed mean based on it has asymptotic variance achieving a Cramer-Rao lower bound in one heavy tail distribution; (c) an improvement of the quantiles-based control chart by Grimshaw & Alt (1997) Grimshaw, S. D. and Alt, F. B. 1997. Control charts for quantile function values. Journal of Quality Technology, 29: 1–7. [Taylor & Francis Online] [Google Scholar] is discussed; (d) Monte Carlo simulations of two new scale estimators based on symmetric quantiles also support this new quantile.