In the design of artifacts that interact with people, the spatial dimensions of the user population are often used to size and engineer the artifact. The variability in body dimensions (called "anthropometry") is used to indicate how much adjustability or how many sizes are required to accommodate the intended user population. However, anthropometry is not the only predictor of these kinds of interactions. For example, two vehicle drivers with similar body dimensions might have very different preferred locations for the seat. The variability not predicted by body dimensions can be considered "preference". Well-conceived models considering all sources of variability can can facilitate the application of design automation tools such as optimization and robust design methodologies, resulting in products that are safer, cost effective, and more accessible to broader populations (including people with disabilities). In contrast, poor models and those that fail to include a preference component can produce misleading results that under- or over-approximate accommodation and prescribe inappropriate amounts of adjustability. This paper reviews common methods of designing for human variability, demonstrating the use and strengths and weaknesses of each. This is done in the context of a simple, univariate case study to determine the appropriate allocation of adjustability to achieve a desired accommodation level.