ABSTRACT
D. G. Simpson and B. H. Margolin discuss procedures for quantal assay data involving toxicity of the substance tested at high doses and a resulting non-monotonic dose-response relationship, as results for the high doses. Typically the new extended models which have been proposed improve the fit of models to data for extreme doses, as they employ tolerance distributions with more flexible tails and of more flexible shape than those of the simpler two-parameter models. B. J. T. Morgan et al. describe a computer package called QUAD, which fits the logit model to raw doses or to specified transformed doses, performs score tests for the cubic-logistic and Aranda-Ordaz asymmetric models and also fits either of these models if necessary. P. Goedhart found the Aranda-Ordaz symmetric model difficult to fit, and also objected to the particular shapes resulting for the tolerance distributions, with some being over a finite range and others with infinite range.
