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

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.