Design and Analysis for Bioassays

Definition. An assay is a form of biological experiment; but the interest lies in comparing the potencies of treatments on an agreed scale, instead of in comparing the magnitude of effects of different treatments. This makes assay different from varietal trials with plants and feeding trials with animals, or clinical trials with human beings. The experimental technique may be the same, but the difference in purpose will affect the optimal design and the statistical analysis. Thus, an investigation into the effects of different samples of insulin on the blood sugar of rabbits is not necessarily a biological assay; it becomes one if the experimenter’s interest lies not simply in the changes in blood sugar, but in their use for the estimation of the potencies of the samples on a scale of standard units of insulin. Again, a field trial of the responses of potatoes to various phospatic fertilizers would not generally be regarded as an assay; nevertheless, if the yields of potatoes are to be used in assessing the potency of a natural rock phosphate relative to a standard superphosphate, and perhaps even in estimating the availability of phosphorus in the rock phosphate, the experiment is an assay within the terms of the description given herein.