RELATING ISOBOLOGRAMS TO RESPONSE SURFACES

The interaction index, isobologram and the appropriate contour of cons tant response of a dose response surface each offer essentially equiva lent information regarding departures from additivity in a chemical co mbination. The benefit of relating the interaction index and isobologr ams to a contour of a fitted dose response surface is that departures from additivity can be related to parameters of a statistical model. T his permits an assessment of the statistical significance of the param eters and conclusions regarding the nature of departures from additivi ty which account for the variability inherent in the experiments used to generate the data. Relationships between statistical models and exp erimental designs can be exploited to yield economical designs for stu dying chemical combinations.