The maximally exposed individual--comparison of maximum likelihood estimation of high quantiles to an extreme value estimate.
The dose to human and nonhuman individuals inflicted by anthropogenic radiation is an important issue in international and domestic policy. The current paradigm for nonhuman populations asserts that if the dose to the maximally exposed individuals in a population is below a certain criterion (e.g., <10 mGy d(-1)) then the population is adequately protected. Currently, there is no consensus in the regulatory community as to the best statistical approach. Statistics, currently considered, include the maximum likelihood estimator for the 95th percentile of the sample mean and the sample maximum. Recently, the investigators have proposed the use of the maximum likelihood estimate of a very high quantile as an estimate of dose to the maximally exposed individual. In this study, we compare all of the above-mentioned statistics to an estimate based on extreme value theory. To determine and compare the bias and variance of these statistics, we use Monte Carlo simulation techniques, in a procedure similar to a parametric bootstrap. Our results show that a statistic based on extreme value theory has the least bias of those considered here, but requires reliable estimates of the population size. We recommend establishing the criterion based on what would be considered acceptable if only a small percentage of the population exceeded the limit, and hence recommend using the maximum likelihood estimator of a high quantile in the case that reliable estimates of the population size are not available.
Wilson
Machelle D
MD
Savannah River Ecology Lab, University of Georgia, USA. wilson@srel.edu
McCormick
William P
WP
Hinton
T G
TG
D000818:Animals; D001699:Biometry; D001822:Body Burden; D002588:Cesium Radioisotopes / Q000493:pharmacokinetics; D004781:Environmental Exposure; D005399:Fishes; D005507:Food Contamination, Radioactive; D006801:Humans; D016013:Likelihood Functions; D009010:Monte Carlo Method; D011835:Radiation Protection; D018570:Risk Assessment
D002588:Cesium Radioisotopes