88 research outputs found
Supplemental Material, appendix - Generalized Inflated Discrete Models: A Strategy to Work with Multimodal Discrete Distributions
No full textSupplemental Material, appendix for Generalized Inflated Discrete Models: A Strategy to Work with Multimodal Discrete Distributions by Tianji Cai, Yiwei Xia, and Yisu Zhou in Sociological Methods & Research</p
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Slogans and Opposition Political Culture: Online Discourse in Iran's Green Movement
No full textIn this study I investigate the Iranian Green Movement supporters' use of slogans as political discourse on the Persian-language opposition website www.kaleme.com. Data was collected from the website's Kaleme section in the form of 22 articles and 3,500 user comments. A coding scheme was constructed to measure the presence of categories and themes in the site's comments section. Findings support the propositions of narrative theorists (e.g. Franzosi, 1998; Benford, 1993) that frequent use of slogans in the comments may reflect a unique cultural element of Persian-language political discourse and reinforce the Green Movement's narrative of opposition to the government
gidm: A command for generalized inflated discrete models
No full textIn this article, we describe the gidm command for fitting generalized inflated discrete models that deal with multiple inflated values in a distribution. Based on the work of Cai, Xia, and Zhou (Forthcoming, Sociological Methods & Research: Generalized inflated discrete models: A strategy to work with multimodal discrete distributions), generalized inflated discrete models are fit via maximum likelihood estimation. Specifically, the gidm command fits Poisson, negative binomial, multinomial, and ordered outcomes with more than one inflated value. We illustrate this command through examples for count and categorical outcomes
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Modeling Place Vulnerability of HIV/AIDS in Texas
No full textThis study provides a measurable model of the concept of place vulnerability for HIV/AIDS that incorporates both community and structural level effects using data provided at the ZIP code level from the Texas Department of State Health Services. Sociological literature on the effects of place on health has been growing but falls short of providing an operational definition of the effects of place on health. This dissertation looks to the literature in medical/health geography to supplement sociology’s understanding of the effects of place on health, to the end of providing a measurable model. Prior research that has recognized the complexity of the effects of place still have forced data into one scale and emphasized individual-level outcomes. A multilevel model allows for keeping the associated spatial unit data, without aggregating or parsing it out for convenience of model fit. The place vulnerability model proposed examines how exposure, capacity and potentiality variables all influence an area’s HIV/AIDS count. To capture the effects of place vulnerability at multiple levels, this dissertation research uses a multilevel zero-inflated poisson (MLZIP) model to examine how factors measured at the ZIP code and county both affect HIV/AIDS counts per ZIP code as an outcome. Furthermore, empirical Bayes estimates are mapped to display how well the model fits across the state of Texas. Limitations of this research include the need to incorporate time, more specific predictors, and individual level factors. The methodology developed permits a more thorough understanding of place effects on the spatial variation of HIV/AIDS
TO WEIGHT OR TO ADJUST: AN EMPIRICAL STUDY OF THE DESIGN-BASED AND MODEL-BASED APPROACHES
No full textWhen a sampling design is correlated to the dependent variable, then the distribution of the sampled units is different from that obtained from a simple random sampling design. Then the sampling design is informative, in the sense that if the design variables were not included in the analysis model, even conditional on the covariates, the estimated model parameters can be biased. Questions have been asked about how survey data are modeled when sampling designs are informative. Two fundamental methodologies, design-based and model-based, have been proposed to address this issue. A model-based method--so-called sample distribution method, has been proposed by Krieger and Pfeffermann (1992; 1997) to extract the model of the sample data as a function of the model holding in the population and the sampling design. Once the model holding in the sample data is derived, the standard model-based analysis techniques can be applied to estimate the unknown population parameters. The core topic of this dissertation is to assess various modeling strategies and estimators of regression coefficients and their variance--both design-based and model-based, in particular, the sample distribution method, under the informative sampling design, and to develop a modeling strategy for analysts who are facing this design-based or model-based dilemma. The dissertation is comprised of three research papers that provide 1) an evaluation of the design-based and model-based estimators under a single-stage informative sampling design; 2) an assessment of design-based and model-based estimators under an informative two-stage clustering sampling design; 3) a joint treatment of informative sampling and unit dropouts in longitudinal studies. When a single-stage sampling design is informative, the model-based naïve method--either ordinary least square or maximum likelihood, produces biased results. The design-based method reduces the amount of biases for some parameters (e.g. intercept) but increases variances, which may lead to too conservative conclusions. The sample distribution method produces better estimates in the term of having smaller biases and variances than the naïve and design-based methods. Under an informative two-stage clustering sampling design, ignoring the sampling effect, the model-based naïve method produces biased results. Under some specific assumptions, , the sample distribution method produces better estimators in terms of smaller biases and higher coverage rates compared to the naïve method and the design-based multilevel pseudo likelihood method. Although many previous studies have shown that multilevel pseudo likelihood method is preferred to compensate for the sampling design, this study shows that a rather simpler method--the sample distribution method can be used to address the design effect. In a specific statistical setting, the relative performance of the design-based and the model-based methods for compensating the informative sampling design and dropout has been investigated. The simulation results indicate that both the model-based and the design-based approaches generally work well in the missing at random and missing not at random settings. Moreover, the sample distribution method combined with the Diggle and Kenward model has advantages of correcting the design effect and the nonignorable dropout.Doctor of Philosoph
Book Review: Congdon, Peter. 2006. Bayesian Statistical Modeling. 2nd ed. West Sussex, England: John Wiley. 596 pp. $110.00. ISBN 100470018755
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Optimal Transport for High Energy Physics
No full textHigh energy physics, like many other scientific disciplines, has entered an exciting new era of big data, where both particle accelerators at the \emph{energy frontier} and astrophysical surveys at the \emph{cosmic frontier} are producing an enormous amount of data which may hold the very key to the most fundamental questions about nature. Mining such gold inevitably calls for revolutionary designs of ever more powerful and efficient statistical analysis frameworks, while at the same time scientific rigorousness places an additional requirement on the interpretability of any novel model proposed. Among a plethora of available modern machine learning techniques, the theory of \emph{optimal transport} stands out as a distinct approach that is both high performing and mathematically well grounded. By equipping the space of data represented as distributions with a suitable metric, optimal transport replaces \emph{ad hoc} notions of similarity with a well-defined distance, opening up a range of new applications with profound theoretical implications. This thesis introduces the theory of optimal transport with an eye towards its usage in physics. Special emphasis is put on two particular optimal transport distances which enjoy unique geometric properties. Utilizing their geometric structure, we develop a computationally efficient linearization framework for the two distances and highlight their approximations for discrete distributions encountered in practice. We then showcase the power of this linearized optimal transport framework by applying it to two use cases---one in collider physics at the energy frontier and the other in dark matter astrophysics at the cosmic frontier. As the adoption of optimal transport in high energy physics is still in its early stage, the present thesis invites the readers to think of other potential applications for their own research
Obesity and the timing of cohabitation and marriage
No full textThe prevalence of adult overweight and obesity has increased substantially in the United States over the past few decades. Besides the health consequences of obesity, it also has social and psychological consequences. As a social marker, it influences individuals' positions or status in a various social contexts and thereby contributes to social stratification. Using The National Longitudinal Study of Adolescent Health (Add Health) data, this paper analyzes the effect of obesity on the likelihood and timing of union formation (marriage and cohabitation) among young adults. The research questions are: Does obesity affect union formation such as cohabitation and marriage? If obesity affects union formation, what are the mechanisms through which it does so? We found that before controlling possible confounding variables, obese young adults will have lower likelihood of entering cohabitation and marriage. After controlling those variables, the difference between obese and non-obese young adult becomes non-significant, but those who are over weighted have higher likelihood to marry and cohabit
Parental involvement, adolescents' self‐determined learning and academic achievement in Urban China
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