8 resultados para Marginal structural model

em Digital Commons at Florida International University


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This dissertation addressed two broad problems in international macroeconomics and conflict analysis. The first problem in the first chapter looked at the behavior of exchange rate and its interaction with industry-level tradable goods prices for three countries, USA, UK and Japan. This question has important monetary policy implications. Here, I computed to what extent changes in exchange rate affected prices of consumer, producer, and export goods. I also studied the timing of these changes in these prices. My results, based on thirty-four industrial prices for USA, UK and Japan, supported the view that changes in exchange rates significantly affect prices of industrial and consumer goods. It also provided an insight to the underlying economic process that led to changes in relative prices. ^ In the second chapter, I explored the predictability of future inflation by incorporating shocks to exchange rates and clearly specified the transmission mechanisms that link exchange rates to industry-level consumer and producer prices. Employing a variety of linear and state-of-the-art nonlinear models, I also predicted growth rates of future prices. Comparing levels of inflation obtained from the above approaches showed superiority of the structural model incorporating the exchange rate pass-through effect. ^ The second broad issue addressed in the third chapter of the dissertation investigated the economic motives for conflict, manifested by rebellion and civil war for seventeen Latin American countries. Based on the analytical framework of Garfinkel, Skaperdas and Syropoulos (2004), I employed ordinal regressions and Markov switching for a panel of seventeen countries to identify trade and openness factors responsible for conflict occurrence and intensity. The results suggested that increased trade openness reduced high intensity domestic conflicts but overdependence on agricultural exports, along with a lack of income earning opportunities lead to more conflicts. Thereafter, using the Cox Proportional Hazard model I studied “conflict duration” and found that over-reliance on agricultural exports explained a major part of the length of conflicts in addition to various socio-political factors. ^

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Past HIV interventions have been critiqued for their failure to incorporate relational factors linked to condom use. Furthermore, few studies have focused on the relational context of sexual risk behavior among adolescents at elevated risk for HIV/STI exposure in the context of substance use. Therefore, this study evaluated the influence of three key relational factors (rejection sensitivity, intimacy dating goals, intercourse-related anxiety) salient for understanding condom use among adolescents in outpatient substance abuse treatment in South Florida. Structural equation modeling was used to test relational factors as direct and indirect predictors of condom use. Specifically, the current study investigated the influence of rejection sensitivity and intimacy dating goals on percentage of protected intercourse, with intercourse-related anxiety modeled as a mediator of this association. ^ Results obtained from the hypothesized structural model suggest rejection sensitivity and intimacy dating goals are significant predictors of percentage of protected intercourse. As expected, rejection sensitivity was related to lower levels of percentage of protected intercourse via heightened levels of intercourse-related anxiety and was not related directly to percentage of protected intercourse. Intercourse-related anxiety was indicated as a partial mediator between rejection sensitivity and percentage of protected intercourse. In contrast, intimacy dating goals was related to lower levels of percentage of protected intercourse directly. The findings demonstrate the importance of relational factors in condom use among adolescents in outpatient substance abuse treatment. Levels of protected intercourse are likely to increase when relational factors are targeted among adolescents in this high-risk population. Implications for prevention strategies targeting this high-risk subgroup of adolescents are discussed. ^

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In the current study, 226 international students attending Florida International University responded to an Web-based questionnaire that assessed self-reported scores for: acculturation, acculturative stress, alcohol use patterns, perceived peer alcohol use, and perceived injunctive social norms for alcohol use. The purpose of the study was to evaluate structural relations among this set of variables using Structural Equation Modeling (SEM) via AMOS 17.0. The results of SEM analyses documented acceptable fit of a model which hypothesized that relations between acculturation and alcohol use variables are mediated partially by acculturative stress, perceived peer alcohol use, and perceived injunctive social norms. While significant path coefficients were documented for paths between (a) acculturation and acculturative stress and (b) acculturative stress and alcohol use, the coefficients had negative signs, contrary to existing studies investigating these relations among immigrant youth. While paths between (a) perceived peer alcohol use or (b) perceived injunctive social norms and participants’ alcohol use were significant, path coefficients between acculturation and either (a) perceived peer alcohol use or (b) perceived injunctive social norms were not statistically significant. In addition, multiple-group comparisons suggested that social support had a significant moderating influence on several significant paths in the structural model. Specifically, international students reporting higher social support reported lower scores for acculturative stress and alcohol use, in contrast to their counterparts who reported lower scores for social support.

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This research examined the factors contributing to the performance of online grocers prior to, and following, the 2000 dot.com collapse. The primary goals were to assess the relationship between a company’s business model(s) and its performance in the online grocery channel and to determine if there were other company and/or market related factors that could account for company performance. ^ To assess the primary goals, a case based theory building process was utilized. A three-way cross-case analysis comprising Peapod, GroceryWorks, and Tesco examined the common profit components, the structural category (e.g., pure-play, partnership, and hybrid) profit components, and the idiosyncratic profit components related to each specific company. ^ Based on the analysis, it was determined that online grocery store business models could be represented at three distinct, but hierarchically, related levels. The first level was termed the core model and represented the basic profit structure that all online grocers needed in order to conduct operations. The next model level was termed the structural model and represented the profit structure associated with the specific business model configuration (i.e., pure-play, partnership, hybrid). The last model level was termed the augmented model and represented the company’s business model when idiosyncratic profit components were included. In relation to the five company related factors, scalability, rate of expansion, and the automation level were potential candidates for helping to explain online grocer performance. In addition, all the market structure related factors were deemed possible candidates for helping to explain online grocer performance. ^ The study concluded by positing an alternative hypothesis concerning the performance of online grocers. Prior to this study, the prevailing wisdom was that the business models were the primary cause of online grocer performance. However, based on the core model analysis, it was hypothesized that the customer relationship activities (i.e., advertising, promotions, and loyalty program tie-ins) were the real drivers of online grocer performance. ^

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This study examined peer relationships and psychosocial functioning as a function of maternal and paternal involvement and nurturance along with the moderating effects of gender, family form, and ethnicity. Prior research has shown the influence of mother’s involvement on peer relationship quality but not of fathers. Further, previous studies did not examine moderation by family form, gender, or ethnicity. The sample consisted of 1359 students who identified their biological mother and father as the most influential parental figures in their lives. Their ages ranged from 18 to 26; Sixty-one percent of the sample was Hispanic, 13% non-Hispanic Black, 25% non-Hispanic White; 76% female and 70% from intact families. The analytical strategy included using bivariate correlations and structural equation modeling to examine these relationships. ^ All dimensions of maternal and paternal nurturing and involvement were positively related to positive characteristics of peer relationships, self-esteem and life satisfaction consistent with the multicultural findings of PARTheory (Rohner, Khalique, & Cournoyer, 2005). A structural model was developed that was able to adequately account for the relationship between parental influence, peer relationships, and psychosocial functioning. These effects of both maternal and paternal influence were strongly moderated by culture, family form, and gender. Finally, a differential effect was found among parental influence with fathers having a greater influence on friendship quality and importance than mothers, despite greater maternal involvement. ^ These findings have theoretical, clinical, and social implications as they call for a socially based theoretical perspective within which to study these relationships. Such a perspective would better inform clinicians when using impaired social functioning as indicative of axial diagnosis, and for the implementation of social policy to encourage paternal involvement. ^

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I conducted this study to provide insights toward deepening understanding of association between culture and writing by building, assessing, and refining a conceptual model of second language writing. To do this, I examined culture and coherence as well as the relationship between them through a mixed methods research design. Coherence has been an important and complex concept in ESL/EFL writing. I intended to study the concept of coherence in the research context of contrastive rhetoric, comparing the coherence quality in argumentative essays written by undergraduates in Mainland China and their U.S. peers. In order to analyze the complex concept of coherence, I synthesized five linguistic theories of coherence: Halliday and Hasan's cohesion theory, Carroll's theory of coherence, Enkvist's theory of coherence, Topical Structure Analysis, and Toulmin's Model. Based upon the synthesis, 16 variables were generated. Across these 16 variables, Hotelling t-test statistical analysis was conducted to predict differences in argumentative coherence between essays written by two groups of participants. In order to complement the statistical analysis, I conducted 30 interviews of the writers in the studies. Participants' responses were analyzed with open and axial coding. By analyzing the empirical data, I refined the conceptual model by adding more categories and establishing associations among them. The study found that U.S. students made use of more pronominal reference. Chinese students adopted more lexical devices of reiteration and extended paralleling progression. The interview data implied that the difference may be associated with the difference in linguistic features and rhetorical conventions in Chinese and English. As far as Toulmin's Model is concerned, Chinese students scored higher on data than their U.S. peers. According to the interview data, this may be due to the fact that Toulmin's Model, modified as three elements of arguments, have been widely and long taught in Chinese writing instruction while U.S. interview participants said that they were not taught to write essays according to Toulmin's Model. Implications were generated from the process of textual data analysis and the formulation of structural model defining coherence. These implications were aimed at informing writing instruction, assessment, peer-review, and self-revision.

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In the current study, 226 international students attending Florida International University responded to an Web-based questionnaire that assessed self-reported scores for: acculturation, acculturative stress, alcohol use patterns, perceived peer alcohol use, and perceived injunctive social norms for alcohol use. The purpose of the study was to evaluate structural relations among this set of variables using Structural Equation Modeling (SEM) via AMOS 17.0. The results of SEM analyses documented acceptable fit of a model which hypothesized that relations between acculturation and alcohol use variables are mediated partially by acculturative stress, perceived peer alcohol use, and perceived injunctive social norms. While significant path coefficients were documented for paths between (a) acculturation and acculturative stress and (b) acculturative stress and alcohol use, the coefficients had negative signs, contrary to existing studies investigating these relations among immigrant youth. While paths between (a) perceived peer alcohol use or (b) perceived injunctive social norms and participants’ alcohol use were significant, path coefficients between acculturation and either (a) perceived peer alcohol use or (b) perceived injunctive social norms were not statistically significant. In addition, multiple-group comparisons suggested that social support had a significant moderating influence on several significant paths in the structural model. Specifically, international students reporting higher social support reported lower scores for acculturative stress and alcohol use, in contrast to their counterparts who reported lower scores for social support.

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This research examined the factors contributing to the performance of online grocers prior to, and following, the 2000 dot.com collapse. The primary goals were to assess the relationship between a company’s business model(s) and its performance in the online grocery channel and to determine if there were other company and/or market related factors that could account for company performance. To assess the primary goals, a case based theory building process was utilized. A three-way cross-case analysis comprising Peapod, GroceryWorks, and Tesco examined the common profit components, the structural category (e.g., pure-play, partnership, and hybrid) profit components, and the idiosyncratic profit components related to each specific company. Based on the analysis, it was determined that online grocery store business models could be represented at three distinct, but hierarchically, related levels. The first level was termed the core model and represented the basic profit structure that all online grocers needed in order to conduct operations. The next model level was termed the structural model and represented the profit structure associated with the specific business model configuration (i.e., pure-play, partnership, hybrid). The last model level was termed the augmented model and represented the company’s business model when idiosyncratic profit components were included. In relation to the five company related factors, scalability, rate of expansion, and the automation level were potential candidates for helping to explain online grocer performance. In addition, all the market structure related factors were deemed possible candidates for helping to explain online grocer performance. The study concluded by positing an alternative hypothesis concerning the performance of online grocers. Prior to this study, the prevailing wisdom was that the business models were the primary cause of online grocer performance. However, based on the core model analysis, it was hypothesized that the customer relationship activities (i.e., advertising, promotions, and loyalty program tie-ins) were the real drivers of online grocer performance.