LC50 estimates and their confidence intervals derived for tests with only one concentration with partial effect.

Nelly van der Hoeven*

TNO Institute of Environmental Sciences, P.O. Box 6011, 2600 JA Delft, Schoemakerstraat 97, Delft, The Netherlands.

Corresponding Author:
Nelly van der Hoeven,
ECOSTAT,
Vondellaan 23,
2332 AA Leiden,
The Netherlands
tel.: (+)31-(0)71-5315011; fax: (+)31-(0)842-116988;
email: NvdH @iecostat.nl

Summary

Linear approximation fails to determine the likelihood based confidence interval for the LC50 parameter in a toxicity experiment with only one concentration causing partial mortality. An equation for this confidence interval is derived given a log-logistic concentration response relation. A table of the 95 and 99% confidence intervals is given for the case that partial survival occurs only at one concentration, under the condition that a fixed number of animals is used at each test concentration and a constant ratio is used between the test concentrations.

keywords: LC50 estimates; confidence intervals; ecotoxicity

logo ECOSTAT Water Research 25: 401-408, 1991