An experiment in which the level of one and only one predictor variable is manipulated. For example, in an experiment assessing price sensitivity, there may be four treatments:
The single factor may be a composite of other variables. For example, in a concept test, each of the concepts may vary in terms of the general description, price, size, and any number of other factors. However, the nature of a single-factor experiment is that when the single-factor is a composite of other variables it is not possible via statistical analysis to disentangle and isolate the relative contribution of these factors (although in many concept tests open-ended questions and standard batteries of questions are commonly used to attempt to disentangle the effect of the various variables).