Triangulating empirical and analytic techniques for improving number entry user interfaces

Empirical methods and analytic methods have been used independently to analyse and improve number entry system designs. This paper identifies key differences in exploring number entry errors combining laboratory studies and analytic methods and discusses the implications of triangulating methods to more thoroughly analyse safety critical design. Additionally, a previously presented analytic method used to analyse number entry interfaces is generalised to analyse more types of number entry systems. This paper takes number entry to mean interactively entering a numeric value, as opposed to entering a numeric identifier such as a phone number or ISBN. Many applications of number entry are safety critical, and this paper is particularly motivated by user interfaces in healthcare, for instance for specifying drug~dosage.