' . , i ON THE USE OF A CORRELATED BINOMIAL MODEL FOR THE ANALYSIS OF CERTAIN TOXICOLOGICAL

In certain toxicological experiments with laboratory animals, the outcome of interest is the occurrence of dead or malformed fetuses in a 'litter. Previous investigations have shown that the simple one~ parameter binomial and Poisson models generally provide poor fits to this type of binary data. In this paper, a type of correlated bino~ mial model is proposed for use in this situation. First, the model is described in detail and is shown to have certain theoretical advantages over a beta-binomial model proposed by Williams [8]. These two-parameter models are then contrasted as to goodness of fit to some real~life data. Finally, numerical examples are given in which likelihood ratio tests based on these models are employed to assess the significance of treatment-control differences.