Information Technology Reference
In-Depth Information
In a review of the application of user models to evaluate Army systems, Booher
and Minninger ( 2003 ) report many instances where millions of dollars over the
course of a device's lifetime were saved by better interface design, through
reduced training, for example. They also highlight several cases where systems
had to be scrapped or modified at great expense because they were not usable.
Use of machines that have different modes can often mislead users into making
errors. Photocopier machines that can be used to send faxes have a common
problem. The default mode of these machines is to copy, but users may not realize
this. Users may type in the area code (say, the U.S. area code 415) as the starting
point for sending a fax, but the copier interprets this as a request to make 415
copies of the document that the user intended to send as a fax! More explicit
displays and more intelligent systems might attempt to catch this type of error.
Photocopies may be relatively cheap, but this type of problem with airline tickets,
machine tools, or photographic films quickly become expensive.
1.3.3 Benefit 3: Safer Systems
Much of the work that has made airplanes the safest transportation per passenger
mile (Gigerenzer 2004 ) has gone into supporting pilots and air traffic controllers to
avoid and, more importantly, catch and recover from errors. This has led to a
drastic decrease in accidents previously ascribed to 'pilot error'. As the cause of
these accidents were typically attributed to well-trained and alert pilots, it is fairer
to diagnose these errors as poor fits between the pilot's capabilities and the
machine at particular times and for particular sets of tasks. Improving this fit thus
improved airplane safety.
Medicine provides a rich source of examples too. For instance, interfaces that
allow users (e.g., nurses) to type in the digits of a drug dose are inherently more
dangerous than those that force users to dial them in using a wheel for each digit
(Pew and Mavor 2007 ). When typing, a repeated digit can increase the dosage by a
factor of ten. This type of mistake is not possible with a dial-based interface.
Medical X-ray machines are powerful devices and often offer little margin for
error. In addition to their technical requirements, they can have usability problems
because their effects are not directly and immediately visible. In the case of radi-
ation treatments for cancer, multiple professionals are involved in their use, from
the oncologists and radiologists who specify the treatment, the technicians who
administer it, to the physicists who maintain it. There are many examples of where
interface design for treatment using X-ray machines and other medical devices
have ignored the user's capabilities, tasks, context, or some combination of these,
and this has led to loss of life. Perhaps the most famous case is the Therac 25
(Leveson and Turner 1993 ). Between 1985 and 1987 there were six known acci-
dents involving massive radiation overdoses with the Therac. Notably, such acci-
dents rarely arise from a single cause. The user interface was only one of several
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