Designing Touch Screen Numeric Keypads: Effects of Finger Size, Key Size, and Key Spacing

Abstract

Designing numeric keypads for point-of-sale devices to optimize keying speed and accuracy while efficiently utilizing touch screen real estate is a challenge. Existing design guidelines for touch screens are applicable to only specific classes of devices and fail to consider user variables such as finger size. The present study investigated keying speed and error rates for various keypad configurations in a simulated retail keying task. Finger sizes were taken into account. Results support the use of compressed (2 mm or less) interkey spacing in keypad designs. No significant effects of key size were found. Gender differences in keying speed and accuracy were explained by finger size differences between males and females. Implications for the design of touch screen user interfaces in point-of-sale applications are discussed.