The logistic regression procedure is a popular statistical method used when analyzing quantal dose-response data. However, logistic regression results based on a poorly designed experiment can be seriously compromised. Our results indicate that depending on the spacing of the doses, the number of doses, and the number of replications at each dose, the user can get very misleading results including ineffective lack-of-fit tests and severely biased coefficient estimates along with biased estimates of response. In addition variance formulas based on asymptotic theory may be completely inappropriate. Simulation results are used to support these statements.
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