Effects of key size and key layout on numeric data entry performance with touch screens

Touch screen displays are prevalently used in a variety of devices ranging from personal mobile devices to public kiosk for information access or self-service nowadays. In most circumstances, a numeric keypad is utilized as an input device and it competes with other displayed information for the limited screen space, underlying the importance of optimizing the design of keypads for improved usability. The present study examined the effects of key size (large: 20 × 20 mm, and small: 14 × 14 mm)-and key layout (fixed and random) with a numeric data entry task. The performance measures were entry speed, accuracy rate, and completion rate. The results showed that the large key size yielded significantly better keying performance than the small key size in all the three performance measures, and female participants had significantly faster entry speed than male participants for the small but not the large key size. Participants responded significantly faster to the telephone-like fixed layout than to the random layout. No significant effects of key layout on accuracy rate and completion rate were found. Design recommendations and considerations for numeric data entry tasks on touch screen devices are provided. © 2014 Taylor & Francis Group, London.