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Models for the estimation of a ‘no effect concentration’
Author(s) -
Pires Ana M.,
Branco João A.,
Picado Ana,
Mendonça Elsa
Publication year - 2002
Publication title -
environmetrics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.68
H-Index - 58
eISSN - 1099-095X
pISSN - 1180-4009
DOI - 10.1002/env.501
Subject(s) - statistics , estimation , point estimation , interval estimation , mathematics , daphnia magna , confidence interval , normality , econometrics , computer science , medicine , economics , management , toxicity
The use of a no effect concentration (NEC), instead of the commonly used no observed effect concentration (NOEC), has been advocated recently. In this article models and methods for the estimation of an NEC are proposed and it is shown that the NEC overcomes many of the objections to the NOEC. The NEC is included as a threshold parameter in a non‐linear model. Numerical methods are then used for point estimation and several techniques are proposed for interval estimation (based on bootstrap, profile likelihood and asymptotic normality). The adequacy of these methods is empirically confirmed by the results of a simulation study. The profile likelihood based interval has emerged as the best method. Finally the methodology is illustrated with data obtained from a 21 day Daphnia magna reproduction test with a reference substance, 3,4‐dichloroaniline (3,4‐DCA), and with a real effluent. Copyright © 2002 John Wiley & Sons, Ltd.