The distribution of random determinants

The exact distribution of |Δn| where Δn is a random determinant with independent and identically distributed exponential elements is given for the cases n = 2 and 3. From the investigation of the behaviour of the density functions for these cases it is conjectured that for any fixed n, the probability density of |Δn| for large values of the argument is the same as the density of (Y/n)ⁿ, where Y is a gamma random variable.     

A model of the adoption of radio frequency identification technology: The case of logistics service firms

Globalization and advances in information technology represent both realities and opportunities for enterprises in the 21st century. This paper aims to broaden understanding of service innovation as a critical organizational capability through which the adoption of information technology influences firm performance. This study examines how the adoption of radio frequency identification (RFID) technology influences the operational performance of logistics service firms. We develop the RFID adoption model based on the interorganizational information systems (IOS) view of the firm that integrates the various strands of research into the framework. The study draws from the related information technology and interorganizational information systems literatures to explore organizational factors associated with the adoption of RFID. A model of the associations between information technology and interorganizational information systems use, social support, power structure, organizational readiness, procedural flexibility, and top management support is developed, and hypotheses are advanced about the relationships among these constructs. An empirical survey was conducted among 500 logistics service firms in Taiwan. A total of 131 valid observations were analyzed using the partial least squares technique. Results showed that RFID adoption has positive effects on business practices, which in turn improves operational performance. We address the value of certain interactive firm behaviors in RFID adoption and identify related constructs of RFID adoption in terms of their efficiency and value for logistics service firms. These results have implications for both education and practice.     

The Freshman 15—A Closer Look

Abstract

Objectives and Participants: Changes in body weight, composition, and size were examined in college freshmen at the beginning (initial, n = 240) and end of fall semester 2007 (n = 214) and the end of spring semester 2008 (n = 205). Methods: Height, weight, body composition, and waist and hip measurements were assessed. Results: Mean weight, body mass index (BMI), absolute and percent body fat all increased significantly over fall semester and the academic year. About 31% of freshmen lost ≥5 lbs. Mean academic year weight gain was 2.6 lbs (entire group) and 6.0 lbs (weight gainers); body fat increased by 4.4 lbs in the weight gainers. A significant correlation (r = .509) was found between weight change and waist circumference change, but not between weight change and waist to hip ratio change. Conclusions: Freshmen weight gain is associated with increases in body fat and waist circumference, which may be troublesome should the trend continue throughout college.     

Conditional Cash Transfer Programs,Credit Constraints,and Migration

This paper models the effect of anti‐poverty conditional cash transfer programs on labor migration. Their effect on migration depends on both the size and type of transfers. Conditional transfers, where the potential recipient has to comply with some requirement in order to qualify for eligibility, may decrease contemporaneous migration for some households, but increase future migration for others. In contrast, unconditional grants may increase current migration.     

Remittances,growth and poverty: New evidence from Asian countries

The present study re-examines the effects of remittances on growth of GDP per capita using annual panel data for 24 Asia and Pacific countries. The results generally confirm that remittance flows have been beneficial to economic growth. However, our analysis also shows that the volatility of capital inflows such as remittances and FDI is harmful to economic growth. This means that, while remittances contribute to better economic performance, they are also a source of output shocks. Finally, remittances contribute to poverty reduction – especially through their direct effects. Migration and remittances are thus potentially a valuable complement to broad-based development efforts.     

Combining multi‐observer information in partially rank‐ordered judgment post‐stratified and ranked set samples

This paper develops two sampling designs to create artificially stratified samples. These designs use a small set of experimental units to determine their relative ranks without measurement. In each set, the units are ranked by all available observers (rankers), with ties whenever the units cannot be ranked with high confidence. The rankings from all the observers are then combined in a meaningful way to create a single weight measure. This weight measure is used to create judgment strata in both designs. The first design constructs the strata through judgment post‐stratification after the data has been collected. The second design creates the strata before any measurements are made on the experimental units. The paper constructs estimators and confidence intervals, and develops testing procedures for the mean and median of the underlying distribution based on these sampling designs. We show that the proposed sampling designs provide a substantial improvement over their competitor designs in the literature. The Canadian Journal of Statistics 41: 304–324; 2013 © 2013 Statistical Society of Canada     

Hausman-type tests for individual and time effects in the panel regression model with incomplete data

By comparing estimators of the variance of idiosyncratic error at different robust levels, two Hausman-type test statistics are respectively constructed for the existence of individual and time effects in the panel regression model with incomplete data. The resultant test statistics have several desired properties. Firstly, they are robust to the presence of one effect when the other is tested. Secondly, they are immune to the non-normal distribution of the disturbances since the distributional conditions are not needed in the construction of the statistics. Thirdly, they have more robust performances than the main competitors in the literature when the covariates are correlated with the effects. Additionally, they are very simple and have no heavy computational burden. Joint tests for both of the two effects are also discussed. Monte Carlo evidence shows that the proposed tests have desired finite sample properties, and a real data analysis gives further support.     

Truncated regular vines in high dimensions with application to financial data

Using only bivariate copulas as building blocks, regular vine copulas constitute a flexible class of high‐dimensional dependency models. However, the flexibility comes along with an exponentially increasing complexity in larger dimensions. In order to counteract this problem, we propose using statistical model selection techniques to either truncate or simplify a regular vine copula. As a special case, we consider the simplification of a canonical vine copula using a multivariate copula as previously treated by Heinen & Valdesogo ( 2009 ) and Valdesogo ( 2009 ). We validate the proposed approaches by extensive simulation studies and use them to investigate a 19‐dimensional financial data set of Norwegian and international market variables. The Canadian Journal of Statistics 40: 68–85; 2012 © 2012 Statistical Society of Canada     

Interim analysis of clinical trials based on urn models

Clinical trials usually involve efficient and ethical objectives such as maximizing the power and minimizing the total failure number. Interim analysis is now a standard technique in practice to achieve these objectives. Randomized urn models have been extensively studied in the literature. In this paper, we propose to perform interim analysis on clinical trials based on urn models and study its properties. We show that the urn composition, allocation of patients and parameter estimators can be approximated by a joint Gaussian process. Consequently, sequential test statistics of the proposed procedure converge to a Brownian motion in distribution and the sequential test statistics asymptotically satisfy the canonical joint distribution defined in Jennison & Turnbull (Jennison & Turnbull 2000. Group Sequential Methods with Applications to Clinical Trials, Chapman and Hall/CRC). These results provide a solid foundation and open a door to perform the interim analysis on randomized clinical trials with urn models in practice. Furthermore, we demonstrate our proposal through examples and simulations by applying sequential monitoring and stochastic curtailment techniques. The Canadian Journal of Statistics 40: 550–568; 2012 © 2012 Statistical Society of Canada     

论"中日15年战争观"在日本的产生及形成

在日本的中国现代史及日中关系史学界,一些人将1931年9月至1945年8月的中日战争称为15年战争,这个观点称15年战争观,即认为“九.一八”事变是中日战争的开端,中日战争是15年。15年战争观的提出有着深刻的历史背景;多数日本学者肯定15年战争观,并以此为前提,论述了中日战争的性质,重点阐明了日本帝国主义是侵略者;对15年战争的称谓,也有人持有异议,其目的在于掩盖日本侵华罪行,为侵略战争辩护,从而否认日本对外侵略的历史。