Some Statistical Techniques for Bio-efficacy Trials

Biological assays and probit analysis are quite useful in designing of bio-efficacy trials and analysis of experimental data. A biological assay (bioassay) is a set of techniques relevant to the comparisons between the biological strength of alternative but similar biological stimuli (for example, a vitamin, a drug, a mental test, a physical force, an insecticide, plant extract, etc.) based on the responses produced by them on the subjects, such as subhuman primates' (or human) living tissues, plants or isolated organs, insects, etc. Normally two preparations of the stimulus, one of known strength (standard preparation) and another of unknown strength (test preparation), both with quantitative doses are applied to a set of living organisms. The general objective of bioassays is to draw statistically valid conclusions on the relative potency of the test preparation with respect to the standard one. Usually when a drug or a stimulus is applied to a subject it induces a change in some measurable characteristic that is designated as the response variable. In this setup, the dose may have several chemically or therapeutically different ingredients, while the response may also be multivariable. Thus the stimulus-response or dose-response relationships for the two preparations, both subject to inherent stochastic variability, are to be compared in a sound statistical manner so as to cast light on their relative performance with respect to the set objectives.