Power Transformation Towards Linear or Partially Linear Quantile Regression Models

99 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005.In this thesis, we consider a family of parametric power transformations for the dependent variable such that a linear or partially linear quantile regression model holds after transformation. The two models being considered are the power-transformed linear quantile regression model and power-transformed partially linear quantile regression model, respectively. We use a cusum process of residuals to measure lack of fit for a given quantile function. A power transformation is chosen to minimize the lack of fit. For the power-transformed linear quantile regression model, we show that the proposed estimator is consistent and asymptotically normal under some mild conditions. We demonstrate that the proposed approach works better than competing methods in the presence of heteroscedasticity and heavy-tails. Inferences about the transformation parameter and about the covariate effects are considered mathematically as well as empirically. A test for the adequacy of the power-transformation models is also proposed. For the power-transformed partially linear quantile regression model, we establish the consistency property for the proposed estimator.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Power Transformation Towards Linear or Partially Linear Quantile Regression Models

99 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005.In this thesis, we consider a family of parametric power transformations for the dependent variable such that a linear or partially linear quantile regression model holds after transformation. The two models being considered are the power-transformed linear quantile regression model and power-transformed partially linear quantile regression model, respectively. We use a cusum process of residuals to measure lack of fit for a given quantile function. A power transformation is chosen to minimize the lack of fit. For the power-transformed linear quantile regression model, we show that the proposed estimator is consistent and asymptotically normal under some mild conditions. We demonstrate that the proposed approach works better than competing methods in the presence of heteroscedasticity and heavy-tails. Inferences about the transformation parameter and about the covariate effects are considered mathematically as well as empirically. A test for the adequacy of the power-transformation models is also proposed. For the power-transformed partially linear quantile regression model, we establish the consistency property for the proposed estimator.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Abstract TP72: The PRISMS Trial: Baseline Characteristics of the First 100 Subjects

Introduction: Ischemic stroke patients with mild deficits were largely excluded from pivotal trials of IV rt-PA. The balance of benefit versus risk of intravenous thrombolysis for this large, understudied patient cohort is uncertain. The PRISMS trial is underway to test the benefit of IV rt-PA for treatment of mild stroke. Objective: To characterize baseline features of the first 100 patients enrolled in this prospective cohort of exclusively mild stroke. Methods: The PRISMS trial is a Phase 3b, double-blind, 75-center, 948-subject study evaluating IV rt-PA administered within three hours of mild stroke onset to improve 90-day functional outcome (modified Rankin Scale 0 or 1). Mild stroke is defined as NIHSS ≤5 and not “clearly disabling” (i.e., inability to return to work or perform basic activities of daily living based on current deficits). Patients are randomized 1:1 to IV rt-PA 0.9 mg/kg with aspirin placebo or IV rt-PA placebo with aspirin 325 mg. Here we describe baseline characteristics, including clinical presentations by NIHSS item, of the first 100 enrolled patients. The study team remains fully blinded to patient treatment assignment and outcomes. Results: The 100th subject was enrolled on June 15, 2015. Baseline characteristics are presented in the Table. Median NIHSS was 2 (IQR 1-3). Clinical presentations of each patient by abnormal NIHSS items are shown in the Figure. Dysarthria, facial palsy, and sensory loss were the most common deficits. Conclusions: This initial 100-patient PRISMS cohort is consistent with expectations. Upon completion, the PRISMS trial will determine the benefit of IV rt-PA for mild stroke