Abstract: A convenient three-parameter class of asymmetric dose-response models can be obtained by raising the logistic response function to the power m, for m>0. For these models, called power logistic quantal response models, D-optimal two point designs for various choices of m are numerically derived. We then investigate design efficiencies and design robustness to misspecification of the three model parameters for two point designs relative to the D-optimal two point design. It turns out that if the experimenter assumes an incorrect value of m when determining a design, the loss of efficiency incurred as result is fairly small for a wide range of m, assuming no error in the initial values of the other parameters. Moreover, the effects of poor initial values of the other parameters seem more serious when m is large than when m is small, so that special care should be taken when m is large.
Key words and phrases: Bioassay, quantal response model, D-optimal design.