Transcript Fix the deelete key!

Fix the deelete key!
Harold Thimbleby1 – [email protected]; Paul Cairns2 –
1 College of Science, Swansea University; 2 Department of Computer Science, University of York
Many infusion pumps and other medical devices have a delete key. The delete
key is provided because manufacturers think users will make mistakes they will
want to correct. It is ironic that the delete key is faulty on every medical device
inspected, as well as on many other products. The examples in this poster are
typical consumer calculators, as often used for drug dose calculations.
–NaN
 The delete key on this Casio calculator ignores
decimal points. If the user keys 1••[Delete]75, they
will enter 75 — and the printed paper record will be
75, not the 1.75 they think they had entered. Like
medical devices, the log would be inappropriate to
use in court: at best, it is a record of what the
device did, not what the user instructed it to do.
 The Hewlett Packard “Easy Calc 100” isn’t easy. It
has numerous user interface defects, including a
flawed delete key.
 Delete (swipe left or
right) on Apple’s iPhone
calculator (iOS 8.3) is
completely broken —
shown here displaying
“not a number.”
 Results of simulating a user noticing and correcting
errors with varying probability, showing the consequential
out-by-ten error probability (i.e., a measure of expected
patient harm). The Casio and HP designs do poorly (top line),
while various redesigns lead to improvement (lower lines).
 Improvement visualised as the ratio of improved
divided by original expected harm (more improvement
increasing upwards on the graph). The less likely a user
notices error (i.e., going left on the horizontal axis) for
any reason, the more dramatic the improved designs
are in reducing expected harm. When the user is
“perfect” (i.e., going right on the graph) improving the
design has marginal effect because the user is also
managing even the device’s design errors.