The logistic and integrated normal binary response curves are known to agree closely except in the tails. For experiments based on three dose levels the power of a signifacance test is found for the null hypothesis that the response curve is ligistic against the alternative that it is normal, and vice versa. From this an appropriate spacing of dose levels for discrimination is found. Approximately 1000 observations are necessary for even modest sensitivity.
Chambers et al. (1967) studied this question.