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271.
This paper proposes a new factor rotation for the context of functional principal components analysis. This rotation seeks to re-express a functional subspace in terms of directions of decreasing smoothness as represented by a generalized smoothing metric. The rotation can be implemented simply and we show on two examples that this rotation can improve the interpretability of the leading components. 相似文献
272.
This paper introduces a finite mixture of canonical fundamental skew \(t\) (CFUST) distributions for a model-based approach to clustering where the clusters are asymmetric and possibly long-tailed (in: Lee and McLachlan, arXiv:1401.8182 [statME], 2014b). The family of CFUST distributions includes the restricted multivariate skew \(t\) and unrestricted multivariate skew \(t\) distributions as special cases. In recent years, a few versions of the multivariate skew \(t\) (MST) mixture model have been put forward, together with various EM-type algorithms for parameter estimation. These formulations adopted either a restricted or unrestricted characterization for their MST densities. In this paper, we examine a natural generalization of these developments, employing the CFUST distribution as the parametric family for the component distributions, and point out that the restricted and unrestricted characterizations can be unified under this general formulation. We show that an exact implementation of the EM algorithm can be achieved for the CFUST distribution and mixtures of this distribution, and present some new analytical results for a conditional expectation involved in the E-step. 相似文献
273.
Estimation of the time-average variance constant (TAVC) of a stationary process plays a fundamental role in statistical inference for the mean of a stochastic process. Wu (2009) proposed an efficient algorithm to recursively compute the TAVC with \(O(1)\) memory and computational complexity. In this paper, we propose two new recursive TAVC estimators that can compute TAVC estimate with \(O(1)\) computational complexity. One of them is uniformly better than Wu’s estimator in terms of asymptotic mean squared error (MSE) at a cost of slightly higher memory complexity. The other preserves the \(O(1)\) memory complexity and is better then Wu’s estimator in most situations. Moreover, the first estimator is nearly optimal in the sense that its asymptotic MSE is \(2^{10/3}3^{-2} \fallingdotseq 1.12\) times that of the optimal off-line TAVC estimator. 相似文献
274.
Both approximate Bayesian computation (ABC) and composite likelihood methods are useful for Bayesian and frequentist inference, respectively, when the likelihood function is intractable. We propose to use composite likelihood score functions as summary statistics in ABC in order to obtain accurate approximations to the posterior distribution. This is motivated by the use of the score function of the full likelihood, and extended to general unbiased estimating functions in complex models. Moreover, we show that if the composite score is suitably standardised, the resulting ABC procedure is invariant to reparameterisations and automatically adjusts the curvature of the composite likelihood, and of the corresponding posterior distribution. The method is illustrated through examples with simulated data, and an application to modelling of spatial extreme rainfall data is discussed. 相似文献
275.
In analyzing interval censored data, a non-parametric estimator is often desired due to difficulties in assessing model fits. Because of this, the non-parametric maximum likelihood estimator (NPMLE) is often the default estimator. However, the estimates for values of interest of the survival function, such as the quantiles, have very large standard errors due to the jagged form of the estimator. By forcing the estimator to be constrained to the class of log concave functions, the estimator is ensured to have a smooth survival estimate which has much better operating characteristics than the unconstrained NPMLE, without needing to specify a parametric family or smoothing parameter. In this paper, we first prove that the likelihood can be maximized under a finite set of parameters under mild conditions, although the log likelihood function is not strictly concave. We then present an efficient algorithm for computing a local maximum of the likelihood function. Using our fast new algorithm, we present evidence from simulated current status data suggesting that the rate of convergence of the log-concave estimator is faster (between \(n^{2/5}\) and \(n^{1/2}\)) than the unconstrained NPMLE (between \(n^{1/3}\) and \(n^{1/2}\)). 相似文献
276.
277.
The accelerated failure time (AFT) models have proved useful in many contexts, though heavy censoring (as for example in cancer survival) and high dimensionality (as for example in microarray data) cause difficulties for model fitting and model selection. We propose new approaches to variable selection for censored data, based on AFT models optimized using regularized weighted least squares. The regularized technique uses a mixture of \(\ell _1\) and \(\ell _2\) norm penalties under two proposed elastic net type approaches. One is the adaptive elastic net and the other is weighted elastic net. The approaches extend the original approaches proposed by Ghosh (Adaptive elastic net: an improvement of elastic net to achieve oracle properties, Technical Reports 2007) and Hong and Zhang (Math Model Nat Phenom 5(3):115–133 2010), respectively. We also extend the two proposed approaches by adding censoring observations as constraints into their model optimization frameworks. The approaches are evaluated on microarray and by simulation. We compare the performance of these approaches with six other variable selection techniques-three are generally used for censored data and the other three are correlation-based greedy methods used for high-dimensional data. 相似文献
278.
Following up on a research note by Stephen Moore published in 1985, this article compares the results of the survey conducted
in 1985 against one carried out in 2006 on the views of eminent social scientists (economists, political scientists, psychologists,
sociologists, historians and anthropologists) on immigration issues. Specifically, the surveys report on whether the respondents
are likely to favor an increase in the number of immigrants who are allowed into the United States and other issues such as
whether immigrants improve the economy.
Rita J. Simon is a sociologist who earned her doctorate at the University of Chicago. She is currently a “University Professor” in the School of Public Affairs and the Washington College of Law at American University, Washington, DC. Professor Simon has authored 37 books and edited 19 including: Immigration the World Over with James P. Lynch. She served as editor of The American Sociological Review and from 1983–1986 as editor of Justice Quarterly. In 1966, she received a Guggenheim Fellowship. Jennifer Kanaan is a doctoral candidate in Justice, Law and Society at American University in Washington, DC. 相似文献
Rita J. SimonEmail: |
Rita J. Simon is a sociologist who earned her doctorate at the University of Chicago. She is currently a “University Professor” in the School of Public Affairs and the Washington College of Law at American University, Washington, DC. Professor Simon has authored 37 books and edited 19 including: Immigration the World Over with James P. Lynch. She served as editor of The American Sociological Review and from 1983–1986 as editor of Justice Quarterly. In 1966, she received a Guggenheim Fellowship. Jennifer Kanaan is a doctoral candidate in Justice, Law and Society at American University in Washington, DC. 相似文献
279.
Sima Zalcberg 《Gender Issues》2007,24(3):13-34
Women’s modesty norms are often perceived as governing women’s bodies and as patriarchal oppression. This study challenges
these perspectives, offering a deeper, multi-dimensional picture showing that the reality of the women’s life is much more
complicated. The article chose to discuss aspects of modesty among women of one of the most extreme Jewish ultra-Orthodox
groups, and in particular, to investigate how they experience an extremely demanding requirement—shaving off the hair on their
head upon marriage and covering their head with a black kerchief. The findings show that there are a variety of voices among
the women, ranging from the view that these practices are desirable, through the view that they empower the women, to the
view that they damage one’s attractiveness and are quite painful.
相似文献
Sima ZalcbergEmail: |
280.
Ester Carolina Apesoa-Varano 《Qualitative sociology》2007,30(3):249-274
This article examines the formation of occupational identity in a nursing program. The normative and ideological dimensions
of this process are revealed in the program’s goals and the views of educators and students through qualitative data from
observations and 30 in-depth interviews. Educators seek to socialize students toward professionalism to raise the occupation’s
status by emphasizing the scientific and technical basis of nursing. Yet students uphold a gendered discourse by identifying
a normative dimension of caring as central to their occupational identity. The dilemma between professionalism and caring
is reconciled as students construct an occupational identity based on “educated caring,” where these two dimensions are equally
valuable and significant.
Ester Carolina Apesoa-Varano is a Ph.D. candidate in the Department of Sociology at the University of California, Davis. Her areas of interest include work, occupations, and professions, medical sociology, gender, and inequality. She is currently working on her dissertation, entitled “Medicine and Caring: Healthcare Providers at Work.” Her previous research focused on a historical analysis of ideologies in the official publication of a large nursing organization. In 2004, a version of her qualifying paper “A Professional Project: Science, Caring, and Ideology in a Baccalaureate Nursing Program” was awarded the Graduate Student Paper Award from the Carework Network (an American Sociological Association affiliate organization). In 2004 she also co-authored with Charles Varano an article entitled “Nurses and Labor Activism in the United States: The Role of Class, Gender, and Ideology,” published in a special issue of Social Justice. 相似文献
Ester Carolina Apesoa-VaranoEmail: |
Ester Carolina Apesoa-Varano is a Ph.D. candidate in the Department of Sociology at the University of California, Davis. Her areas of interest include work, occupations, and professions, medical sociology, gender, and inequality. She is currently working on her dissertation, entitled “Medicine and Caring: Healthcare Providers at Work.” Her previous research focused on a historical analysis of ideologies in the official publication of a large nursing organization. In 2004, a version of her qualifying paper “A Professional Project: Science, Caring, and Ideology in a Baccalaureate Nursing Program” was awarded the Graduate Student Paper Award from the Carework Network (an American Sociological Association affiliate organization). In 2004 she also co-authored with Charles Varano an article entitled “Nurses and Labor Activism in the United States: The Role of Class, Gender, and Ideology,” published in a special issue of Social Justice. 相似文献