Grouping of Printed Digits for Manual Entry

Abstract

Recent studies on the spatial grouping of the digits are reviewed with emphasis on six new experiments by the author. For several tasks including keyboard entry and telephone dialing, grouping by 3's and 4's is consistently best in speed. Differences in error rate are generally statistically insignificant. If successive numbers have different groupings (user cannot predict grouping), differences between groupings may not be found. Users often state preferences for larger groups than those producing best performance. The temporal grouping of the user's keystrokes reflects the spatial grouping on the source document; however, the number of digits keyed after each look or referral to a number is not necessarily an indication of optimum grouping. All data point to grouping by 3's and 4's as best.