Record Display for the EPA National Library Catalog


Main Title Regression on Medians of Probability Distributions.
Author Sumler, M. R. ; Fisher, H. L. ; Hall, L. L. ;
CORP Author ManTech Environmental Technology, Inc., Research Triangle Park, NC.;Health Effects Research Lab., Research Triangle Park, NC.
Publisher 1991
Year Published 1991
Report Number EPA-68-02-4450; EPA/600/D-91/048;
Stock Number PB91-177006
Additional Subjects Lethal dose 50 ; Toxic tolerances ; Carcinogenesis ; Epidemiology ; Regression analysis ; Survival analysis ; Dose-response relationships ; Mortality ; Probabilistic estimation ; Statistical Analysis System(SAS)
Library Call Number Additional Info Location Last
NTIS  PB91-177006 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 20p
The median is a fundamental parameter in the area of lifetime and survival statistics. In toxicodynamics the LD50, lethal dose that results in 50% mortality, is frequently used. The median is also used to describe the incidence of cancer and other disease states. Factors such as nutritional status, age of animal, and exposure to a second chemical can cause the LD50 to shift. It is therefore desirable to determine a functional relationship between the median of a distribution and a cofactor. The paper used SAS to examine the use of median regression to predict a continuous dependent variable as a function of a single cofactor and compare these results to the standard ordinary least squares regression techniques. Two data sets were generated using the SAS RANUNI and NORMAL functions. In one, the median line was proportional to the mean line, and both the median and mean had positive slopes with respect to a cofactor. In the other, the slope of the median line was positive while that of the mean line was negative.