Glossary - Foundations for Designing User-Centered Systems - page 417

Task-action mapping Describes the relationship between the domain of the task
and the domain of actions. Ideally there should be a simple and direct mapping
between the two.
THEA (Technique for human error assessment) Method for analyzing erro-
neous performance using an iterative process. Like the CREAM it assumes that
the context is a major influence on performance.
THERP (Technique for human error rate prediction) An approach to mod-
eling errors in human performance. The probability of errors occurring is
conditioned by performance shaping factors as a way of taking into account the
context in which the error happens.
Threshold The smallest energy level in a stimulus that can be detected by a user.
Tower of Hanoi A task used to study problem solving. It has three pegs or posts,
and disks, typically three to eight, but in theory there could be any number of
disks.
Transfer (of learning) Where learning on one task has an effect (either positive
or negative) on a task that is performed later.
Upper limb disorders (ULD) Aches, pains, tension, and disorders that involve
any part of the arm from fingers to shoulder or neck. They include problems
with the soft tissues, muscles, tendons, and ligaments, as well as with the
circulatory and nerve supply to the limbs. Often caused or exacerbated by work
and, particularly, repetitive work. They lead to conditions such as repetitive
strain injuries.
Usability A multi-faceted concept used to represent how easy a system is to use,
how easy it is to learn to use, how safe it is, how effective (and efficient) it is,
and how satisfying it is to use.
Usability testing A term usually restricted to describe the evaluation of the
usability of a system under controlled (laboratory) conditions.
User experience (UX) The user's perceptions and responses that result from the
use or anticipated use of a product, system or service. Some people regard UX
as representing a broader view than usability.
User-centered design (UCD) An approach that focuses on the user's needs,
carrying out an activity/task analysis as well as general requirements analysis,
performing early testing and evaluation and designing iteratively.
Users Generally refers to people who use artifacts (systems, devices, and so on).
There are several types of user, including operators, pilots, and drivers.
Validity A term used to refer to whether the particular measure that you are using
is really measuring what it is supposed to be measuring. There are several types
of validity.