The IEEE summary of this error is worth a read, both from the cause and the outcome of the UI testing.
Since I’m frequently dealing with interfaces that require typing of sets of digits or numbers. I’ve been thinking about this for the last few days and have two thoughts on how to reduce errors like this. Not of course that I have any capabilities to test either idea, but there’s always a chance that somebody has some additional insight.
The core summary of the error is:
Fossbakk’s daughter’s account number was 71581555022, but she inserted an extra 5 and keyed in 71581555 5022. The user interface accepted only 11 digits in this field (the standard length of a Norwegian account number), thus truncating the number to 71581555502. The last digit is a checksum based on a modulo-11 formula. This will detect all single keying errors and errors where two consecutive digits are interchanged. Inserting an extra 5 changed both the ninth and tenth digits.
Ideas of how to reduce the error:
Grouping of digits
Telephone numbers most specifically, are traditionally written in different grouping combinations (nn nn nn nn OR nnn nnn nnnn). While bank numbers are usually just strings of digits. Thus providing very few visual cues that there is an error, in a grouped system you would notice that the first digit of a group is incorrect. Though I will say that windows product keys, which are grouped are a total pain, but they at least provide a quick way to see that any one group is ok.
Mixed digits and alpha
If a account number was a mixture of digits an alphabetic characters (avoiding those that might be misleading 0 vs. O), I would imagine that similar to the grouping strategy it would reduce the error rate. Things like: 715 BUVX 5022, one could even extend this to be similar to the old US telephone system nomenclature “715 wabash 5022” where technically only the “WAB” is the unique part, but by turning into a real word the error rate might be reduced.