Abstract
We propose a methodology of representing quantitative user diversity as intervals and conducting their calculations using interval arithmetic to evaluate, compare and optimize design ideas considering quantitative user diversity in a general and systematic manner. The proposed methodology and implemented software are applied to two simplified design problems considering quantitative user diversity: a design of a button height on a wall and a design of three dimensional layouts of cellular phone buttons. Through calculation results and a simple user test, we confirmed that the proposed methodology and implemented software can yield adequate information and hints for universal design.
