Inferences on regression coefficients in a regression model under heteroscedasticity and robustness with respect to departure from normality

In this paper we consider a simple linear regression model under heteroscedasticity and nonnormality. A statistical test for testing the regression coefficient is then derived by assuming normality for the random disturbances and by applying Welch's method. Some Monte Carlo studies are generated for assessing robustness of this test. By combining Tiku's robust procedure with the new test, a robust but more powerful test is developed.     

On the one-sample location hypothesis for mixed bivariate data

We study a hypothesis testing problem involving the location model suggested by Olkin and Tate (1961). Specifically, we derive a likelihood ratio lest of the associated location hypothesis as an alternative to the conventional method of carrying out separate tests for each of the parameters. A small sample Monte Carlo comparison indicates the general superiority of the former in terms of statistical power. We also comment briefly on the properties of the test.     

A more general methodology for fitting global cross-ratio models for discrete longitudinal responses

In this paper, we focus on repeated measurement problems, comprising an interesting research area in statistics. We study longitudinal data which arise when outcomes are observed repeatedly on each experimental subject at several points. We focus on a marginal approach for this type of data with lack of independence among the observations proposed by Dale [Global cross-ratio models for bivariate, discrete, ordered responses. Biometrics. 1986;42(4):909–917] for bivariate, discrete, ordered responses. We propose an alternative estimation based on divergence measures to the full likelihood method proposed in that paper. Finally, a wide simulation study and a data example that illustrates the new methodology is provided.     

Outlier detection by robust principal components analysis

The robust principal components analysis (RPCA) introduced by Campbell (Applied Statistics 1980, 29, 231–237) provides in addition to robust versions of the usual output of a principal components analysis, weights for the contribution of each point to the robust estimation of each component. Low weights may thus be used to indicate outliers. The present simulation study provides critical values for testing the kth smallest weight in the RPCA of a sample of n p-dimensional vectors, under the null hypothesis of a multivariate normal distribution. The cases p=2(2)10, 15, 20 for n=20, 30, 40, 50, 75, 100 subject to n≥p/2, are examined, with k≤√n.     

The Representation of Hypergeometric Random Variables using Independent Bernoulli Random Variables

In this paper, we show that a hypergeometric random variable can be represented as a sum of independent Bernoulli random variables that are, except in degenerate cases, not identically distributed. In the proof, we use the factorial moment generating function. An asymptotic result on the probabilities of the Bernoulli random variables in the sum is also presented. Numerical examples are used to illustrate the results.     

Social Sources of Community Solidarity in U.S. Congregations

Community solidarity, or a collective sense of belonging, plays a vital role in the health and survival of many organizations. Consequently, identifying the elements that contribute to a strong sense of solidarity within communities has long been a topic of inquiry for scholars. In this study, we draw upon prior theorizing to develop and test four hypotheses regarding the organizational characteristics associated with community solidarity in religious congregations. Multivariate models are estimated using national data on religious congregations from the 2001 U.S. Congregational Life Survey (n?=?357). Organizations with greater community solidarity tend to feature higher levels of social capital (operationalized with measures of friendship networks and participation in organizational activities), higher levels of official membership within the organization, and inspiring congregational leadership. Higher levels of commitment are associated with greater community solidarity, but the effect is wholly mediated by social capital. Congregations that engender higher levels of community solidarity share certain organizational features, including higher levels of social capital, higher rates of membership, and inspiring leaders.     

如何有效地扩大医疗保险覆盖面——拉美国家的经验教训及启示

本文以拉美国家的经验及启示为视角，就如何有效地扩大医疗保险覆盖面问题展开论述。     

918年抑或978年——《青史》所载藏传佛教后弘期起始年考

《青史》主张的藏传佛教后弘期起始年是公元978年，而不是918年，这一年代应该置于文本的整个年代记述系统中加以确定和认识。对《青史》所记年代的可靠性应该分期看待，前弘期的诸多年代记载源自汉文史料，但作者使用时却往后误置了一个饶迥60年，而后弘期的诸多记载则基本可信。