The study consisted of an introduction, three scans performed

for each of the eleven scanners, and an adjacent

interview. We utilized a within-subject design. The dependent

variables were task completion time and reliability, by which

we mean the share of successful scans within a task completion

time below 15 seconds. The independent variables were the

barcode scanners as listed in Table 1. For each participant the

study was recorded on video. We also transcribed comments

the participant made during the tasks.