Case Studies - Measuring the User Experience: Collecting, Analyzing, and Presenting Usability Metrics - page 252

those participants indicated that it would be more helpful if the overlay were
directly on the scanner (rather than projected on the monitor). Twenty-eight
participants (35%) did not find the overlay helpful; nine of those participants
indicated that the overlay would be helpful if it were directly on the scanner. Six
participants (7.5%) indicated that the overlay was not a factor, as the process is
quite simple and straightforward; one participant from this group indicated that
it would be more helpful if the overlay were on the scanner.
10.2.2 Discussion
In this study, we examined whether people can perform fingerprint self-captures
successfully using the proposed real-time feedback system. We found that the
participants were very effective and efficient in performing the self-capture tasks
with great satisfaction.
The participant completion rate was high (92.5% in Task 1, then improved
to 100%) with fewer than 11 errors on average. When examining only posi-
tioning errors (errors related to pressure or angles were excluded), the average
errors dropped (mean = 5.94). Fingerprint image quality was comparable, if not
better, to images taken in the attended situation. In a study with an attended
setup, Stanton et al. (2012) reported that the acceptance rates of slaps ranged
from 55 to 63%, based on the US-VISIT acceptance criteria. In this self-capture
study, acceptance rates ranged from 67.5 to 68.4% for slaps, higher than those
in Stanton et al. (2012) .
Using the on-screen instructions, participants were able to position their
hands accordingly, make adjustments when needed, and capture fingerprint
images in approximately 1½ minutes. Ratings on the post-task questionnaire
indicate that the participants felt comfortable and confident and interacted
without much difficulty with the self-capture process. It was clear to the par-
ticipants when the capture process began and ended. In debriefing, participants
indicated that the self-capture process was easy, straightforward, and quick. They
praised the experience of “do-it-yourself” as it gave them a sense of being in con-
trol and being trusted; as one participant put it: “The self capture process was
very neat. It is easy enough that anybody can do it. It is elementary, easy to use,
even children can do it.”
Our second research question was to investigate whether an overlay facili-
tates the self-capture fingerprint process. The overlay condition did not show
consistent advantages or disadvantages of performance, that is, time, errors,
and image quality, over the nonoverlay condition. However, more participants
(57.5%) perceived that having the overlay helped them with the positioning
of their hands and providing visual feedback. One reason for the discrepancy
between performance and preference is the experimental configuration. The
setup required participants to place their hands on the scanner (often looking
down) and look up at the LCD monitor for the fingerprint image and feedback
for corrections if needed. The overlay guide was superimposed onto the screen,
which added another level of hand-eye coordination. Participants realized