Zhou, Tianhong2010-08-132010-08-132010-08-13http://hdl.handle.net/2097/4638The potency of a pesticide or some materials is widely studied in agricultural and biological fields. The level of a stimulus that results in a response by 50% of individuals in a population under study is an important characterizing parameter and it is denoted by the median lethal concentration (LC50) or the median lethal dose (LD50) or median. Estimation of LC50 is a type of quantal response assays that belong to qualitative indirect bioassays. In this report, seven methods of estimating LC50 are reviewed with reference to two normal distributions of tolerance in four different cases. Some modified methods are also discussed. Simulation shows that the maximum likelihood method generally outperforms all other traditional methods, if the true tolerance distribution is available. The comparison results indicate that the modified Dragstedt-Behrens method and modified Reed-Muench method are good substitutes for the original ones in most scenarios.en-USLC50BioassayReportStatistics (0463)