Browsing by Subject "Identification"
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Item ACC 2013, An Airborne Experimental Test Platform: From Theory to Flight Companion Software Package(2014-07-23) Dorobantu, AndreiItem Essays on the Effect of Environmental Factors on Health Choices and Health Behavior of Individuals(2015-07) Katare, BhagyashreeUnderstanding the causes of spread of obesity is important to address public health concern and formulate public policy. Causally identifying factors that influence the spread of obesity is difficult. Specifically, it is difficult to disentangle the contextual effects or environmental factors that drive weight gain in individuals from the self-selection of individuals into groups that share common, potentially unobserved, characteristics. In my first paper I tried to disentangle these competing explanations by collecting data from a unique population of international students. I surveyed international graduate students at 48 public universities across the United States. I used this data to investigate the effect of obesity prevalence in a particular region on international students' weight gain. Results show that students studying in areas with a lower prevalence of obesity show a significantly lower increase in their weight compared to students studying in areas with a higher prevalence of obesity. In the second essay I used the restricted-use New Immigrant Survey 2003 data to study the association between surrounding environmental factors and BMI of recent immigrants to the United States. Immigrants also offer a unique opportunity to disentangle the self-selection and contextual effects while studying the effect of environmental factors on the weight gain in individuals. I find statistically significant effects on the immigrants' BMI levels. Immigrants residing in areas with lower prevalence of obesity have significantly lower BMI levels compared to those residing in areas with higher prevalence of obesity. Results show that dietary change in immigrants is influenced by the local environmental factors and that dietary change affects the BMI levels of the immigrants. The third essay is an intervention study to promote physical exercise among freshman students at a university in the Midwest. I investigated the effect of social norming and financial incentives on promoting physical exercise among randomly selected freshman students. Through the third essay, I investigate the effectiveness of two policies that have been proven to modify individual behaviors in encouraging healthy behavior.Item Identification of Semiparametric Discrete Choice Models(Center for Economic Research, Department of Economics, University of Minnesota, 1989-09) Thompson, T. ScottThe question of model identification is analyzed for the semiparametric random utility model of discrete choice. Attention is focused on settings where agents face a common choice between a set of J+l alternatives, but where actual choices are only partially observed. Necessary conditions are derived for the setting where the only data on actual choices consists of a binary indicator for one of the alternatives. Sufficient conditions are developed in this setting for a linear in parameters specification of indirect utility. It is found that relative to the parametric case, only a mild continuity restriction on the distribution of regressors is needed in the semiparametric model. Under these circumstances all of the choice probabilities are identified, even though actual choices are only partially observed. It is shown that estimators that rely only on the index structure of the model require substantially stronger prior restrictions on the parameters for identification when the number of alternatives is large. Finally, results on the model with partial observability of choices are used to analyze the special case of full observability.Item Semiparametric Instrumental Variable Estimation of Simultaneous Equation Sample Selection Models(Center for Economic Research, Department of Economics, University of Minnesota, 1991-06) Lee, Lung-FeiThe identification and estimation of a semiparametric simultaneous equation model with selectivity have been considered. The identification of structural parameters from reduced form parameters in the semi parametric model requires stronger conditions than the usual rank condition in the classical simultaneous equation model or the parametric simultaneous equation sample selection model. The necessary order condition for identification in the semiparametric model corresponds to the over-identification condition in the classical model. Semiparametric two-stage estimation methods which generalize the two-stage least squares method and the generalized two-stage least squares method for the parametric model are introduced. The semi parametric generalized least squares estimator is shown to be asymptotically efficient in a class of semiparametric instrumental variable estimators.Item Thor Flight 30(2012-02-22) Taylor, BrianItem Thor Flight 31(2012-02-22) Taylor, Brian