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Full-Text Articles in Physical Sciences and Mathematics
Averaged Instrumental Variables Estimators, Yoonseok Lee, Yu Zhou
Averaged Instrumental Variables Estimators, Yoonseok Lee, Yu Zhou
Center for Policy Research
We develop averaged instrumental variables estimators as a way to deal with many weak instruments. We propose a weighted average of the preliminary k-class estimators, where each estimator is obtained using different subsets of the available instrumental variables. The averaged estimators are shown to be consistent and to satisfy asymptotic normality. Furthermore, its approximate mean squared error reveals that using a small number of instruments for each preliminary k-class estimator reduces the finite sample bias, while averaging prevents the variance from inflating. Monte Carlo simulations find that the averaged estimators compare favorably with alternative instrumental-variable-selection approaches when the strength levels …
Mathematics In Forensic Firearm Examination, Erin N. Zalewski
Mathematics In Forensic Firearm Examination, Erin N. Zalewski
Honors Capstone Projects - All
Forensic Science encompasses many disciplines that employ the scientific method to examine, analyze, and interpret physical evidence in the courtroom. The discipline of Forensic Firearm Examination involves the examination and comparison of ballistic evidence components to determine if they came from the same source. In other words, firearm examiners are tasked with determining whether spent cartridge cases or bullets were fired through the same gun. Examination of ballistic evidence can involve the employment of automated matching systems, comparison microscopy, and mathematical analysis. The comparison microscope is the tool of the firearm examiner and allows for the simultaneous view of ballistic …
Estimation Of Heterogeneous Panels With Structural Breaks, Badi Baltagi
Estimation Of Heterogeneous Panels With Structural Breaks, Badi Baltagi
Center for Policy Research
This paper extends Pesaran's (2006) work on common correlated effects (CCE) estimators for large heterogeneous panels with a general multifactor error structure by allowing for unknown common structural breaks. Structural breaks due to new policy implementation or major technological shocks, are more likely to occur over a longer time span. Consequently, ignoring structural breaks may lead to inconsistent estimation and invalid inference. We propose a general framework that includes heterogeneous panel data models and structural break models as special cases. The least squares method proposed by Bai (1997a, 2010) is applied to estimate the common change points, and the consistency …
Estimation And Identification Of Change Points In Panel Models With Nonstationary Or Stationary Regressors And Error Term, Badi H. Baltagi, Chihwa Kao, Long Liu
Estimation And Identification Of Change Points In Panel Models With Nonstationary Or Stationary Regressors And Error Term, Badi H. Baltagi, Chihwa Kao, Long Liu
Center for Policy Research
This paper studies the estimation of change point in panel models. We extend Bai (2010) and Feng, Kao and Lazarová (2009) to the case of stationary or nonstationary regressors and error term, and whether the change point is present or not. We prove consistency and derive the asymptotic distributions of the Ordinary Least Squares (OLS) and First Difference (FD) estimators. We find that the FD estimator is robust for all cases considered.